The trap below was played in Keres-Arlamowski, 1950 and also, as I recall, in a game between Alekhine and four(!) amateurs. There are 12 games with the trap in ChessBase's Big database. In two of them, White missed the mate in one! Back in my 1.e4-playing days, I routinely played 5.Qe2!? in blitz games. More often than not, my opponent fell into the trap! The correct response is 5...Ndf6!