For me it was Ezra Miller showing up in The Flash TV show a few years ago during their big “multiverse” crossover event.
On the big screen, gotta give it to the recent Flash movie. The poorly CGI’d Nic Cage was such a great fan service. Also I managed to square myself from all the media past premier, that G.C. showing up at the end was a pleasant surprise.
Hugh Jackman in X-Men First Class wasn’t totally unexpected, but it was worth a good chuckle.
Gotta be Tom Cruise in tropic thunder for me
Didn’t even realize it was him until the credits rolled
Ed Sheeran in Game of Thrones felt a bit odd.
Adam Savage in The Expanse. I watch that man making stuff in his workshop every week, did a triple take suddenly seeing him appear in the show!
RIP Arboghast
Cecil B. Demented is a John Waters comedy loosely based on the notorious Patty Hearst kidnapping from the 70s.
Patty Hearst has a cameo.
I levitated from my couch when Ahmed Best appeared as Kelleran Beq in The Mandalorian… and nearly lost it when he put Grogu on Jar Jar’s ship.
Commentiquette in It’s Always Sunny