After buying the shoes from Al, Marcy gets up and walks to the door wearing the shoes she just bought. But when Al showed them to her, the shoes were still in the box. She never put them on her feet before she gets up (she showed up at his house barefoot).
Al comes home and announces he won the shoe salesman of the month competition, winning a first class ticket to Hawaii. Peggy then tells him she already called the airline and traded in his ticket for four standby tickets. Peggy couldn't have known Al won until he came home and told them, nor could she have known which airline to call.
While most of the rock stars at the gate mispronounce "Axl Bundy" (Al's rocker alter ego), Robby Krieger calls him "Al" but no one notices.