Sean Gaffney has the titles and descriptions of all 75 cartoons in the upcoming Woody Woodpecker set.
Woody was introduced in an Andy Panda cartoon, hence the subject heading. He's hardly the only popular cartoon character to start out in someone else's cartoon. Popeye's debut cartoon, "Popeye the Sailor," is sort of an early version of a stealth spinoff pilot -- since it launched the character in a Betty Boop cartoon. Daffy Duck, of course, made his debut in a Porky Pig cartoon.
What other theatrical cartoon characters (as opposed to TV cartoons like Yogi Bear) made their debuts with established series cartoon stars?