Cameos/guest stars?

Does anyone have experience using other players as cameos/guest stars in the games they run?

By this, I mean inviting another player into an ongoing game to play the role of a NPC for a very limited time (like a single scene). For instance taking on the role of innkeeper, librarian, obstructive bureaucrat, or something like that.

TV shows can get a lot of mileage out of a good guest appearance. Maybe the same is true for PbP games? I was thinking it could be fun for several reasons, and it could be an opportunity to meet more GPers... and who doesn't want an opportunity to play a large ham?

(I'm not currently running any games, so you can answer without worrying about being press-ganged into a cameo.)

Edit:
I realised that my original question was too restrictive. I'm also interested in hearing from people who haven't tried something like this.
- Would you consider asking another player to join for a cameo role in a PbP game you're running?
- Would it be fun if someone joined as a cameo in a game you're playing in?
- Would you be interested in playing a cameo role in a game?

I did it once in an at-the-table game of Paranoia. One of the players had already played the adventure that I was running before. I know them and they wouldn't meta-game if they were to rejoin the same game a second time, but I thought it would be fun to give them the main NPC instead.

In the starter adventure, this NPC is the guide for the new clones so they stick around throughout the story. That way they could enjoy the same adventure from a different point of view, and it didn't matter that they knew some spoilers. In fact they could play into those spoilers.

I think it worked quite well in this case :)

I was a cameo in some games GM’d by someone I once knew from another site. Morbid humor—he wrote a short series called Splatter-Elf. (Which inspired an indie RPG.)

Why I was the cameo guest star, I don’t know, but it was this weekly Play-by-Chat RPG which was super fun. I didn’t realize I could bang out jokes that fast in a chat room because I never really used the chat feature on the site.

Later, he had me Guest-NPC an RPG called The Endless Hunt and I helped him write the rules. That was like the early 2010s… fun stuff though!

I thought you meant guest-stars like real-world people appearing in the adventure. I do this a lot in my modern horror and pulp campaigns. In my modern horror campaign, the characters got sent back to World War I, where they met J.R.R. Tolkien. I've also had them meet King Charles and some other well-known figures.

Another interpretation of 'cameos', I sometimes used real actors as NPC portraits, it's quite fun...

I realised that my original question was too narrow. I would also like to hear the thoughts of people who haven't tried this yet. I've updated the post.
Nice. That was the sort of thing I was thinking of. At a table, it makes sense to have a guest star for a full session (or even longer), but I PbP I was thinking it could be for a shorter duration (just one scene).
Sounds fun!

I read the play report. Splatter-Elf sounds like weird gory fun (at least for a one-shot).
That also sounds fun. And I think it's almost mandatory if you're doing time travel (like Dr Who).
Nice! I guess the same actors might come up again and again ... just like in real movies.

I can not count the number of times I have been asked to join a game because the GM needs 'an exposition dump character', someone who can uncover the clues they have but their brute-force party does not have the means to find. "We need a wizard type." Or the GM needs 'a GM mouthpiece' that can feed information to the party. "Maybe a Warlock, or Cleric?"

I have never been asked to join a game to take on an NPC (though it is common enough to ask players not in a scene to play an NPC for that scene), nor even a pregen, but that is probably because people know I enjoy character creation and am happy to make something that fits within the parameters they need. (Maybe the Spell-Slinger and Spooky in Monster of the Week for the first type, maybe an Angel (Divine) for the second; a Werewolf bounty-hunter in Urban Shadows; and so many DnD Clerics (and Bards) (for the mouthpiece, but also for the heals:)...)

I have heard of games where they get a player from another/previous game reprise their character over the phone for a scene. This was 'before internet'.

This is somewhat close to "real world"…

I have Samus Aran as a (player-picked) special guest star for the current "episode" in my game that takes place in a video game world.

A few of us tinkered with this idea from time to time back on Tavern Keeper, and while it never -really- landed that I saw, it was fun...

I haven't, but I've often thought it would be fun.

I've fireballed the fourth wall a couple of times and had an NPC take over the DMing for me - like Andy Kaufman's Tony Clifton. In one game the PCs also went through the breached fourth wall and became the players at the table.

I haven't yet invited anyone to guest in my games, but I have been a guest in other games myself - mostly in duets, where I'd be a random NPC for the characters to meet for a single scene.
I also remember a game where the characters were streaming their adventure and any user could pop up in a public chat as a chatter character, so kind of a guest appearance too! (And all of these experiences were facilitated by bowlofspinach. <3)

A while ago I did start a solo game with a public chat system where anyone could sort-of-participate to influence the actions of my characters, but wasn't confident enough to advertise it and kinda archived it to wait for better days. :D
Yes x3! Well, except I'm not running any games where cameos would make sense, but you know, if I were...

Could be a fun experience. More so if the players knew about the character beforehand. Don't know if there would be much impact otherwise. Beyond if they liked the PC turned NPC.

I've had some guest cameos in my 1-1s that the DM has brought in. One was Flying above for some Christmas party shenanigans. The DM (Bowl) runs some others games in the same setting, so occasionally when my characters drop by where another character from a different game works that players pops in for a little bit.

I have also considered asking a player who strongly likes roleplay to do a cameo in a certain pathfinder AP if I run it as I think they would be very good with the assignment for that section, but not enjoy other parts of the AP as its a more combatty one.

So for the questions yes to all as long as it makes sense.