1. P-K4 P-K4 2. P-Q4 PxP? 3. P-QB3and it usually continues: BugHouse, when the attacks on KB7 and the center are aided by the arrival of ChessPawns and ChessKnights from the other board.
In ChesSers, of course, the ChessPawns and ChessKnights aren't quite as likely to be forthcoming so early in the game, and three pawns to one is an almost insurmountable disadvantage for the CheckersSide board which receives the one. For these reasons, when used in ChesSers, the DanishGambit is also known as the "What on Earth did you play?!", after a comment made to that effect when it was first attempted.
As far as I know, it was never tried after that, thankfully!! I have to say that the most interesting thing was the reaction from AndrewSchoonmaker and myself. Andrew was quite confused at my hsyteria, and well I . . . --JoshMiddendorf
At that point, I didn't really understand how the CheckersSide worked, and so I was playing speed chess/bughouse the way I knew how... I may have since ventured the opening, though I don't recall for sure. The version with 4. NxP? might not be quite so broken/painful... --AndrewSchoonmaker