I admit it right from the start. You don’t have to sniff out any Scooby-Doo-like clues to get at the fact of it. For my family D & D game, I steal characters whole. Mostly from things the kids have watched and loved on TV or in the movies.
These mostly ad up to funny side bits and digressions. In the epic chase across the continent of Khorvaire they conducted when the adventure involved chasing a secret-agent vampire who had gone rogue from his government spy service, they had to receive important information at one point from a randomly generated pair of characters. So I stole whole this pair from a Cartoon Network favorite show.
I turned Flapjack and the Captain into a half-elf with a crazed addiction to candy and sweets and a blue goblin capable of mind tricks and random evil that he doesn’t really mean to commit. They have only appeared in one adventure so far, but I kept them around for use again, if the time is right.
Vanellope from Wreck-It Ralph makes a sweet gnome and convenient comic relief character for when you are journeying in the Dark Dimension and visiting places like Castle Ravenloft. I have not actually used her in an adventure yet, but I have one prepared in a haunted cross-dimensional ghost-castle.
And some characters are lifted whole out of game supplements and pre-made adventure books. Some of my favorite characters are things that you were supposed to kill in the adventure, but charmed and made friends with instead. Like the denizens of floating Cloud-Castle Tempest.
The supplement listed the giants of Castle Tempest as being evil and secretly cannibalistic, preferring to eat human adventurers. I turned them into a widow and her cloud-giant kids lost in time (in the game world we are using giants once had a high-technology empire that fell back into dark ages, so I merely had to make them into accidental time travelers). Not all adventures have to be about chopping the heads off monsters and stealing their stuff. A family like this makes for interesting and bizarrely out-of-proportion friendships and troubles.
So, not everything that makes my Dungeon-Master fictions interesting is entirely my own work. Like good comedians everywhere, I am not above stealing a joke.