Houdini Egg Salad is a saying from the Midwest. This phrase stems from a situation in which a male and female fornicating are interrupted by a person(usually another male), who is hiding in the closet. This closet dweller pounces out of the closet, just before the other male is about to "hoagie slap" said female, and the sexing couple is doused with a combination of mustard, mayonnaise, and, of course, hard boiled eggs.
"Did you hear Cory got Houdini Egg Saladed last Thursday?"
"Yeah, I heard Steve used a gallon of Hellman's."