Quotes / Not Allowed to Grow Up

Brian: Look, Stewie, don't you think at some point you're gonna have to let Rupert go? I mean, you are getting a little old to have a teddy bear.
Stewie: Brian, I'm one.
Brian: Still?
Family Guy, "Road to Rupert"

Flapjack: Cool! How did you do that?
Captain K'Nuckles: Eh, I'll tell you when you're older.
Flapjack: When's that going to happen?

"I wish I would grow up; it feels like I've been 10 for years." note 
Anduin Wrynn (or rather his gold coin), World of Warcraft

"Aw Maggie, don't ever turn two."
Lisa Simpson, The Simpsons, "Elementary School Musical"

Lisa: To prolong the run of the series, I was secretly given anti-growth hormones.
"Why aren't I aging? Good God, am I a monster?"
Bart Simpson (while writing on the chalkboard), Robot Chicken, "Major League of Extraordinary Gentlemen"