We've seen a real celebrity appear as themselves on a show for a quick laugh or maybe they take over the entire episode.
An actor might request the latter if they want it to be clearer that this is a purely fictionalized version of themselves. Not to be confused with For Halloween, I Am Going as Myself.
Occasionally, there will be an example of this with a deceased star/famous figure. is Alice playing a character who just happens to be named Alice as well? Supertrope of Newscaster Cameo (newsreader As Himself) and Leno Device (talk-show host As Himself).