#23: Super Mario Bros. 2 (Nintendo, NES, 1988/1989)

At the end of each level of Super Mario Bros. 2, there stands the head of a great bird. It opens its mighty jaw wide, and you step inside, to be consumed, and thusly to enter a new realm. […] To prove yourself worthy to gain access to the gullet of these birds, you must first defeat an opponent in single combat. In most, though not all cases, the gatekeeper you must face down is Birdo, who is described as follows in the game manual: “He thinks he’s a girl. He shoots eggs from his mouth.”