Pretty much what the title says. Those little walk-ons, walk throughs and/or other brief interactions that sometimes pop up in movies and television shows. It could be an actor, a singer, a reality star (ugh) or even the film's director.
In case you're wondering as to the difference between a cameo and a guest star, I'll use the Green Hornet on "Batman" as an example. The first time GH appeared, it was one of the window gags:
That's a cameo (and my entry).
The second time, it was a two part cross-over where their interaction was a (the) major story element.
That's a guest star.
Other than that, the usual rules (size, NSFW, etc.) apply.
Up to three entries per person, please and I'll plan on keeping entries open for five days.
Good luck!
In case you're wondering as to the difference between a cameo and a guest star, I'll use the Green Hornet on "Batman" as an example. The first time GH appeared, it was one of the window gags:

That's a cameo (and my entry).
The second time, it was a two part cross-over where their interaction was a (the) major story element.
That's a guest star.
Other than that, the usual rules (size, NSFW, etc.) apply.
Up to three entries per person, please and I'll plan on keeping entries open for five days.
Good luck!