The misspelling of "Marshall" with two Ls was a meta joke by the writers, as it's a mistake they had seen several times in articles about the show.
The backgammon wiz nicknamed "Falafel" is a real Israeli player, Matvey Natanzon, whom Graham Yost read about in "The New Yorker."
The filming location where Boyd and Johnny meet up is the same hacienda that was featured in the Hallmark movie "Merry Kissmas."