This is sort of a cameo...and a "spin-off" at the same time. The little animal that comes out of the badniks, the blue one was "Flicky Bird". Early on, JUST the bird had a game all to itself. You had to save bird chicks from a cat. However, like many early games, the box art was bonkers & seldom made any sense. In the left game, you see the USA cover. Chicks in sunglasses (never happened in game) & an odd crow-like bird that looked nothing like the game sprite. On the right, you can see the Japanese version, which while slightly more accurate, is also more bizzarre. The bird is using its feathers as a 'fist' to hold a hammer (while it flies.....) as an agitated looking cat runs along the floor. But there's a broken chicken egg, a baby bottle for some reason (all birds are lactose intolerant, for obvious reasons...), a spilling tea cup & a handgun aimed at one of the baby birds. One bird looks like it's biting the cat's tail as they all fly around in front of random shelves. Do either of these covers make you want to play the game?
So, although a minor not-even-a-character, that one bird was used as the main character of a separate game.