Both played straight and averted by the Donkey Kong Country series. While the original Donkey Kong grew old to become Cranky Kong, his wife Wrinkly passed away (though she returnedas a ghost) and Tiny Kong grew up from a little kid to being in her late teens, Diddy and Dixie Kong (who is Tiny's older sister) are still kids after 13 years. Since most of the Kongsnote The only ones known to still be around are Donkey, Diddy, Dixie, Cranky, Funky, and Tiny (A few others are still used as trophies in Super Smash Bros.). were Put on a Bus after Rareware left for Microsoft, it is possible that not as much time has passed in the Donkey Kong universe as in Real Life. Kiddy Kong, the baby character from Donkey Kong Country 3: Dixie Kong's Double Trouble!, has not yet gotten off the bus. It appears that Rare attempted to have Diddy age slightly in Diddy Kong Racing DS, in which his voice was deeper and appeared to have broken.
Drakengard has Seere, a six-year-old boy who made a pact with a golem creature. The price for the pact was being unable to grow up. In Drakengard 2, he is now 24 years old, but still looks like a little boy.
In Ensemble Stars! it's more like 'not allowed to graduate' - the story continuously fills in a roughly one-year period of time covering a single school year, because if time moved on, a third of the characters would leave the school and not be able to participate the same way anymore.
Tori also references this trope off-handedly in one story, complaining about his short height and dreaming of when he'll get taller, but then remembering that since his Charm Point is his unusually youthful looks, there are definitely fans out there who would retort 'no way, you're neeever allowed to get any older!'
Final Fantasy Crystal Chronicles tracks progress by years, with one year passing for every three dungeons cleared. You may have played the game to year 157, but your character's appearance- that of a 12-15 year-old- doesn't change at all.
Final Fantasy Tactics kept track of the ages of characters by how many calendar years had passed since the game began, with one day passing for every location Ramza passes through on the world map. If you spend a lot of time traveling and battling, the three-year-old Prince Orinas may be 20 by chapter 2, but he's still an infant as far as the story (and his appearance) is concerned.
In the self-help app game Finch, all micropets start in their baby forms, with an option in the settings to keep them from growing up. However, once they have already grown to adulthood, they cannot be regressed back to babies.
A justified example occurs in the finale of Ghost Trick. Anybody who is impaled by a shard of the Temsik Meteor no longer ages and is functionally immortal, trapped between life and death; in the original timeline, this happened to Yomiel, who was already an adult, but when Sissel goes back to undo his death, the shard instead impales Sissel himself, who was only a kitten at that point in time. Ten years later, in the present, Sissel is still a kitten.
Huey, Dewey, and Louie. There is no noticeable difference between their appearance in Birth by Sleep and their appearance in Kingdom Hearts II, 11 years later.
In 3D, Riku explains that the different worlds don't operate on the same time scale. Not many fans wanted to believe him, though the Timeless River world from II would at least add some more credence to that theory.
Puyo Puyo: Arle actually does age in-between parent series Madou Monogatari and Puyo Puyo. With that said, the Puyo series has gone on for almost three decades and yet none of its characters show signs of aging (though we at least get some of their adult appearances in Puyo Puyo 7 by way of their Mega transformations). Some of the mages in the series use "anti-aging magic" to retain their youthfulness, so Sega could use that as an explanation should they feel the need.
In The Sims a baby grows up to be a child... and then can never age again, meaning that eventually, they hit their peak grade and can never accomplish anything ever again. The sequels introduced aging and allowed the children to grow up.
In The Sims 2, only the Sims in the household you're currently playing as will age; so unless you regularly switch between households, it will likely end up with your elderly sim's old friends from elementary school still being children.
Averted in The Sims 3 and onwards by default. All the sims in a particular game will age and die, though you can control how long each stage of life is and even turn it off if you want.
In The Sims 4 you can choose a variety of options for who ages, including only the Sims you are currently playing like in The Sims 2, everyone like in The Sims 3, only Sims you've played, or only Sims you haven't played. There is also the option to turn aging off completely.
The Sims Freeplay originally had babies unable to age however updates added in the feature eventually.
Sonic had a birthday in Sonic Generations. He's still fifteen years old. Humorously, before Sonic Adventure, his canon age was sixteen. He seems to be aging backwards! Also in Generations, he, Tails and Eggman are depicted as having aged quite a bit since their 16-bit days, not even being able to fully recall their early adventures in Chemical Plant or Green Hill Zone despite the above. His newest English voice actor as of Sonic Colors uses a noticeably deeper voice than previous ones, however, nothing points to Sonic actually aging.
The series has this trope in spades; none of the characters seem to grow any older than the age in which they were introduced, and some (like Charmy Bee) actually had their ages and mannerisms adjusted to be younger than what they were before.
Amy Rose seems to be an aversion, having aged from 8 to 12 between Sonic CD and Sonic Adventure, which seems reasonable... But is weird alongside Knuckles, who went from 15 to 16; Tails, who remained 8; and Sonic, who, as mentioned above, went from 16 to 15.
Infinite lampshades this in Sonic Forces. He mentions that Sonic and Tails (who are 15 and 8 respectively) have been fighting Eggman for decades.
In Stardew Valley, you can play the game for as many in-game years as you like, but Vincent and Jas will always stay young children, and any children that you might have will never grow older than toddler age.
The Story of Seasons series (formerly known as Harvest Moon) has this through nearly every game; once the child you have reaches a certain age — generally the walking or "child" stage — they never get any older. Village children, if present, also never grow up. Also true of all the other characters, since you can play for hundreds of years in-game and no one ever gets older or dies. Harvest Moon: A Wonderful Life (and its remake, Story of Seasons: A Wonderful Life) avert this, as the theme of the game is to watch your child grow up and see who they become; the local children Kate and Hugh also grow up alongside your child, and everyone ages visibly over the roughly twenty years the game goes on. Harvest Moon: A New Beginning allows your child to become a teenager, but it's through magical candy and they only stay a teen for thirty days before reverting back to a child.
Sakura from Street Fighter is an odd example. She was introduced in the Street Fighter Alpha prequel series as a teenager, and by all rights, should be at least in her early 20's at this point. However, because her Iconic Outfit is a Japanese schoolgirl uniform, Capcom seems to want to avoid aging her up too much and has refused to really address the subject in-game. It's particularly jarring since Karin, Sakura's rival and former fellow high schooler, was finally given an adult redesign in Street Fighter V. It was then averted when Sakura joined Street Fighter V as DLC: She's officially in college and has a part-time job working in an arcade, with her uniform being her new default costume (her iconic sailor fuku is now her nostalgia costume).
