- 2002 (Voiced by Ashley Johnson) - She is 17 years old. She is honest, adventurous, friendly, light-hearted, luminous, confident and relaxed. She looks out for her younger siblings. She loves her family, and she loves to have fun.
- 2003 (Voiced by Nika Futterman) - She is 16 years old. She is quite ditzy and is very forgetful and absent-minded. Despite being ditzy and absent-minded, 2003 is shown to be skilled at fashion designing and making smoothies, which demonstrates that while she may not be very bright, she is creative and artistically inclined. She is also very friendly and gets along well with her siblings. She plays keyboard in the heavy-metal rock band "The Rockin' Rockers", in Season 1 only. She's a foil to 2007. 2007's the sensible, rational, and sophisticated of the duo, while 2003's a complete scatterbrain who's too dumb to think for herself. However, unlike 2007, who's primarily catty, condescending, egotistical, pessimistic, and bossy, 2003 is a well-meaning Nice Girl without a single mean bone in her body. She's also a foil to 2005. 2003 and 2005 have a lot in common in that both are perpetual optimists and Cloudcuckoolanders who often get on others' nerves with their eccentricity but are Innocently Insensitive in their defense; However, 2003 is a Valley Girl caught up in the recent trends, while 2005 is a Kiddie Kid and a Genki Girl who loves having fun and doing gymnastic stunts whenever she's excited.
- 2004 (Voiced by Miranda Cosgrove (Season 1, speaking & singing voice) Karen Malina White (Season 2-Season 4, speaking & singing voice) - She is 15 years old. She is very happy, wild, caring, and easily the loudest sibling of the entire family. What she likes most is singing, playing musical instruments, and being with her family. She has a huge interest in rock music. She is a big fan of several rock groups, and her dream is to become a rockstar. She owns and plays an electric guitar, with which she has proved to be a very good guitarist. Only in Season 1, she formed a band with 2003 & 2005 called "The Rockin' Rockers". She's a foil to 2005. Both 2004 and 2005 are kind-hearted Genki Girls who are Older Than They Look, wear skirts, and even have practically indifferent names sans the numbers being rearranged; however, 2004 is rather mellow, mature, and rational whenever not rocking out, while 2005 is always her cheerful, goofball self. She's also a foil to 2007. Both 2004 and 2007 are brown-haired, rambunctious tomboys who can ham it up pretty good; however, 2007 is by default more jerkish, violent, and mean-spirited, while 2004 is characteristically a Cool Big Sis with a mellow demeanor, she's a lot more nicer, and she has a good grip on reality. She's the one taking 2008 to his elementary school every weekday morning.
- 2005 (Voiced by Janice Kawaye (Season 1 & Season 2) Cristina Milizia (Season 3-5)) - She is 14 years old. She is buoyant, cheerful, bouncy, optimistic, energetic and full of spirit. A young Japanese-American teenage girl who's the cheerleader of the group. She skips through life with a really huge smile and an assortment of extremely colorful clothes, She is the drummer of the band "The Rockin' Rockers" in Season 1 only. She never frowns. She's always smiling every day!!!! She's a foil to 2004. Both 2004 and 2005 are kindhearted Genki Girls who wear skirts, are Older Than They Look, and even have practically indifferent names sans the numbers being rearranged; however, 2004 is rather mellow and rational most of the time when not rocking out, while 2005 is always her cheerful goofball self. She's also a foil to 2003. Both 2003 and 2005 are Cloudcuckoolanders who get on the nerves of others with their excentricity and sometimes behave inappropriately in serious situations, but are Innocently Insensitive in their defense. To boot, both are perpetual optimists who remain cheerful in spite of the world's shortcomings. However, 2003 is a teenage Valley Girl stereotype caught up in the recent trends, while 2005 is the optimist who's obsessed with having fun. She's even a foil to her friend, Lucina. Both girls are interested in pantomime and areas of performance arts, and both are All-Loving Nice Girls. However, their personalities couldn't possibly contrast more strongly. 2005 is cheerful, comedic, wears bright clothes and always enjoys spreading laughter and happiness everywhere. Lucina is a gloomy emo who wears dark clothes. 2005 really hates The Fresh Beat Band with a huge burning passion, and she finds it scary. She's the one taking 2008 home from elementary school every afternoon. The episodes, "Autumn Wonders", "Watch Out for 2007s" "Training Day", "Homecoming Party" and "The Football of Wisdom" show her in her cheerleading outfit.
- 2006 (Voiced by Jennifer Hale (Season 1) Brenda Song (Season 2-Season 4)) - She is 13 years old. She is a gloomy, cynical, deadpan, and mysterious goth girl who is always seen with a stoic frown. She is interested in occultism, poetry, and the works of Gothic authors, like Edgar Allen Poe and H.P. Lovecraft. She frequently uses words to describe her actions, such as saying the word "Sigh" instead of actually sighing. She is the guitarist and lead singer of the band THE SOUL SKÜLLS.
- 2007 (Voiced by Crystal Scales (Season 1) Tania Gunadi (Season 2-Season 4) - She is 12 years old. She is secretive, arrogant, stubborn, sarcastic, and jealous.
- 2008 (Voiced by Tara Strong) - He is the middle child of the family. Just like 2005, he also hates The Fresh Beat Band.
- 2009 and 2010 (Voiced by Jessica DiCicco (Season 1, 2009) Alyson Stoner (Season 2-Season 4, 2009) Grey DeLisle, 2010) - They're twin sisters that say
- everything in unison.
- 2011 (Voiced by Dee Bradley Baker) - She is the baby of the family.
- Lucina (Voiced by Liz Georges) - One of 2005's friends. While both of them like pantomime, they are complete polar opposites. 2005 is upbeat, cheerful, optimistic, and is a Pollyanna, while Lucina is emo, stoic, and depressed. However, they are both nice girls without and mean bones in their body.
- Danny (Voiced by Alexander Polinsky) - One of 2003's friends. He is prone to the fact that he is overcompensating for his family himself, as it's not unusual for him to do this. However, he has a great outlook for all his friends.
Note: In episodes 1 through 3 of Season 1, Pomann Sound did the sound editing. But, in episodes 4 through the remainder of Season 1 (2010-2014), Beatstreet Productions did the sound editing. Then, in Season 2 (2014-2016) & Season 3 (2016-2018), Dick Maitland did the sound editing. And then, in Season 4 (2018-2019) & Season 5 (2019-2020), Sue Robertson & Julia Snell does the soind editing.
- S1E1: "Meet the Years/Year Blower/2008's Day Out with Roberto" - The Year siblings are expected to meet a moving family who are very sweet. 2005 plans to know important things about them./With no dialogue in this episode except for one instance, 2008 and 2005 try to prank 2007 without her knowing./2008 hangs out with his best friend, Roberto.
- S1E2: "2010's Tooth/Get the Message" - 2010 awaits a visit from the Tooth Fairy/2008 leaves a scatching message on 2007's phone.
- S1E3: "Come Home, 2003!/Autumn Wonders" - When 2004 forgets about watching over 2003, and that 2007 ends up yelling at 2003, she runs away from home./It's fall and the year siblings are having fun playing in the colorful leaves. Meanwhile, 2005 delivers love letters all around Yearville on her scooter, especially Grandpop Maine's farm, and also getting ready for her cheerleader event in the high school football game.
- S1E4: "Watch Out for 2007s/Growing Pains" - When 2008's older sister 2007 won't stop picking on him, 2005 decides to help her younger brother by looking in his Great Big Book of Everything to learn about Armadillos: armor-plated champions of defense! From there, 2008 & 2005 both get some ideas on how to deal with 2007's pestering./2005 is dressing up as Hatsune Miku for a costume party, but when 2007 tries it on, it's way too big for her! So 2003 decides to make 2007 a costume she will never forget. Meanwhile, 2005 asks 2008 if she wants to go get the Great Big Book of Everything and look for an animal that grows and enlargens. 2008 cheerfully shouts yes, and they both learn about hermit crabs, who are great at growing and getting new clothes (or skin in that matter).
- S1E5: "Sad Parrot/Electric Night" - 2008 gets a new parrot who is very, very depressed/The Year family want to watch a special TV show, but there's a power cut caused by lightning. ""Note:"" 2005 sings the song "Build Me a Building" in the episode "Electric Night". This song would later be inspired by the Bubble Guppies song by the same name.
- S1E6: "25 Times the Chaos!/Night Vision" - After getting bonked by a tree while in a game of hide and seek, he imagines himself as a rabbit with 15 more siblings./2004 and all her pets all want to get to sleep, but she keeps hearing mysterious noises. 2005 assures her that, "There's nothing to be afraid of, sweetie!", but she still remains convinced that she is hearing an AWFULLY scary monster. She knows that owls can see in the dark and wonders how they do it. She seeks the answer in 2008's "Great Big Book of Everything" in the hope that it will help her to spot the monster so everyone can finally get some sleep.
- S1E7: "Morning Meltdown/Training Day" - In order to get his project to school on time, 2008 works to get each of his sisters out the door during their morning routine./2005 and her friend Peter (Voiced by Joseph Gordon-Levitt) are training for the pep rally at high school.
- S1E8: "2003's Cookies/Captain Obvious" - 2003 tries to deliver cookies for her friend, Danny (Voiced by Alexander Polinsky) while avoiding some obstacles along the way./2007 tries to push 2004 down the stairs, but 2004 won't let her pass!
- S1E9: "Bleep/No Bees for 2003" - 2005 says a curse word, and she breaks stuff repeatedly, so 2008 has to stop her./2003 tries to be a beekeeper so she can stop the bees stinging her.
- S1E10: "Fighting Dilemma/You Can't Beat the Heat" - 2007 hates 2005 a lot. Until one day, she and 2005 have a lot of fun with cleaning the shed./The Year siblings want to go to the pool on a really hot day.
- S1E11: "2007 Fails at Babysitting/Game Night" - 2007 tries to get involved with 2002, 2003, 2004, 2005 and 2008's babysitting club, but the 4 aforementioned older siblings and 2008 don't think 2007 is the nurturing type, so 2005 and 2008 decide to teach 2007 how to properly babysit. Then and there, 2007's first gig is with the McCauley family where she watches Shelly and Mary. The three also babysit more families along the way./Grandpop Maine and Grandma Tooey has a special night planned for the Year siblings, called Game Night.
- S1E12: "There's No Place Like Home/Road Trip!" - A termite infestation has forced the Year family out of their house. While the house is being fumigated, 2003, 2005, 2006, 2008, 2010, 2011, and Grandpop Maine go to Uncle Pterence's cool house where loads of Nick Jr., Sesame Street, and HIT Entertainment VHSs are seen there with a bunch of TVs, cool beds, and a gaming room, while 2002, 2004, 2007, 2009, and Grandma Tooey go to Aunt Mannie, Aunt Mannie forces them to watch her cats, eat old moldy pudding that she offers, and to massage her feet. For this reason, 2002, 2004, 2007, and 2009 don't enjoy her./The Year Family go on a road trip to Weeping Willow Resort & Lodge on Yeary Year Road.
- S1E13: "Homecoming Party/Sing it Loud!" - There's a homecoming party at the high school, so 2005 invites 2008 to have fun with her./In this musical episode, a show called America's Next Hitmaker is holding a song contest for anyone who can come up with a song that the whole world will love. 2004 plans to make an original song for the contest while hearing songs that didn't actually come from her family members and Max.
- S1E14: "Hide and Seek/What Can You Decide?" - The older year siblings and 2008 decide to play hide and seek./2003 decides on what to wear for Picture Day in High School.
- S1E15: "The Un-Party/No Noise is Good Noise" - 2003, 2004, 2005, and 2008 celebrate a birthday party for their dull and dreary aunt Mannie, whose actual idea of a birthday party is equally drab music (instead of a traditional Happy Birthday song), eating a loaf of bread (as opposed to cake), and doing office work (in place of opening presents)./A mysterious noise is interrupting the Rockin' Rockers while they attempt to perform a special song for 2008. The girls must track down the sound and when they do, they find Grandpop Maine playing a musical instrument!
- S1E16: "Access Denied/See You There!" - 2003 desperately wants to look at 2002's diary, but she won't let her look. Overwhelmed, 2003 tries to find ways to look at the diary without 2002 knowing./2008 is going to a party with his friends, but 2003, 2004 and 2005 really need his help for the Rockin' Rockers' new song for the concert they're playing, so he writes their song, and finally gets to go to his party, with 2005 cheerfully shouting, "Have a great time, Linky!".
- S1E17: "The Iguana Sing Along/2008's Great Adventure!" - 2004 learns about iguanas from 2008's Great Big Book of Everything for Animal Show & Tell at high school, and she goes on a search to find something so the iguanas can have a sing along before taking a nap./2008 goes on an excellent adventure with 2005.
- S1E18: "To Catch a Stealer/The Football of Wisdom" - 2002 and 2004 find out that somebody is stealing their valued items and must set out to find them and get the stealer arrested. However, it turns out to be their friends that borrowed them for a day./When 2008 is watching a football game at his older sisters' high school, he miraculously catches the football and just when one of the players was about to get hurt, he sets off and hits the football very hard into the hurdle. 2005, one of the high school cheerleaders, finds out about this and congratulates her younger brother for making that throw. Meanwhile, 2005 and the other sisters throw a party for 2008 for throwing a football very hard, when 2008 is out with his best friend, Roberto for movie night.
- S1E19: "Love is in the Air!/LaNae Seeks Help" - It's Valentine's Day and all of the Year Family are giving valentine cards to everybody/2005 decides to cheer up her best friend, LaNae, after she discovers that her family has depression after her grandpa died.
- S1E20: "Skull ROCK!" - 2006 performs with her band, The Soul Skülls in Lucillina's garage. They rock their hearts out. They perform very wild, very hard, very death-metallish, and very violent, too.
- Tween-Girl as 2002
- Princess (Season 1, singing voice) Amy (speaking voice, Season 2-Season 5 singing voice) as 2003
- Salli as 2004
- Kayla (Season 1) Ivy (Season 2-Season 5) as 2005
- Vixen as 2006
- Kimberly as 2007
- Justin as 2008
- Kendra as 2009
- Salli as 2010
- Kidaroo as 2011