[holbue]

I remember this variation of the story:

An unknown chessplayer bet a lot of money, that he could play live & simultaniously against two grandmasters and achieve at least 1 point. The two matches were played in different rooms next to each other. No one except the unknown player was allowed to switch rooms during the matches (to not disturb the grandmasters). Obviously he played White against one grandmaster, Black against the other, and won his bet.

As I sometimes tell this anecdote, I wonder what its actual source might be?

I'm pretty confident, this never happend in real, as I expect no grandmaster could get scammed that easily. But the story could be rooted in a "catch me if you can"-like movie or novel or something.

If someone knows more, I would be happy for a hint...

[yesenadam]

It's a very old trick I'm sure. As for it never happening or fooling anyone in real life: the magician/mentalist Derren Brown challenged 9 English chess players, including 4 GMs, to a simul on his TV show, and got a plus score - he secretly had 8 of the players playing each other, with whom he thus had an even score. The 9th was president of a university chess club, and a very weak player, who Derren played and beat, winning the match.

https://www.youtube.com/watch?v=rIAXIubSTkc

[i-am-cjc]

Might not be exactly what you're thinking of, but Derren Brown did similar against a group of players

https://en.chessbase.com/post/derren-brown-s-che-trick-once-...