What’s the greatest number of times that players have castled in a single chess game? Surprisingly, the answer is three. From the Irish Chess Journal, November-December 1987:
An amusing incident occurred in this year’s Armstrong Cup between W. Heidenfeld and N. Kerins. Heidenfeld first castled Kingside and then, in face of a strong attack, moved his King back to its original square and then inadvertently castled on the Queen’s side. The incident was unnoticed by both players: the game continued and Kerins went on to win. Wolfgang does not lose many games in Irish chess but he has probably created some sort of a record, in Ireland at least if not elsewhere, by castling on both sides and still losing a tournament game!