"Rascals" was freaking AWESOME. Awesome. I especially love that Alexander is conscripted to help take back the ship with his remote-controlled car.

So, yes, the characters-get-young phenomenon is common, but in this case, mini!Jack actually STAYS young. And gets sent to high school at the end of the episode. Which is horribly cruel to the character, but a nice little present to fanfic writers everywhere.