Chess Opening Theory/1. f4/1...e5/2. fxe5/2...Nc6/3. Nf3/3...g5

3...g5!?
This is a committing and demented-looking move. But it is the a standard move in the From's Gambit. The point of 3...g5 to to play ...g4 and kick the f3-knight away, and to discourage kingside castling by White. However, it is certainly not without consequence.