Since the 1980s and the 2000s, there have been many animated characters which are either junior versions (e.g., children, nephews, nieces, or protégés) or younger versions (i.e., the original characters presented as children) of other well-established characters. An example of a younger character is Scooby-Doo as a puppy, and an example of a junior character is Scrappy-Doo, Scooby-Doo's nephew.
This trend, often referred to as the "babyfication" of shows, was kicked off by the 1984 series Jim Henson's Muppet Babies, which was based on a sequence in the (live-action) film The Muppets Take Manhattan. An earlier example of younger versions of existing cartoon characters, however, would be Bugs Bunny and Elmer Fudd from the 1944 cartoon The Old Grey Hare, which features Bugs and Elmer as babies (as well as very old characters) The same concept was used in a cartoon featuring an elderly Foghorn Leghorn and Barnyard Dawg who each have a grandson, and in a planned scene in the Three Stooges short Three Little Pigskins in which each stooge has an identical son.
Examples from comic books are Superboy, who was introduced in 1944's More Fun Comics #101 as the teenage version of Superman; Superboy would eventually be seen in an animated series in the 1960s and a live action TV series in 1988. Other examples were Little Archie, which featured the childhood adventures of Archie Comics character Archie Andrews, and How Obelix Fell into the Magic Potion When he was a Little Boy, about the character from the French comic book series Asterix.