In The Stinsons, Barney Stinson mentions that the real Karate Kid is William Zabka, not Ralph Macchio. Later, during Barney's bachelor party, Robin Scherbatsky hires William Zabka to dress as a clown, and reveal himself at the end during a ruse. Zabka is shown to later have been invited to Barney and Robin's wedding. He becomes the best man for a short time when Barney is furious at Ted Mosby, but when Barney re-instates Ted, William is shown to be irritated. He later tries to sabotage Ted's best man duties. He later tells Marshall Eriksen that he saw Lily Aldrin leave a convenience store and enter The Captain's car. He follows Ted, Marshall, Barney and Ranjit Singh to The Captain's house so Marshall can punch him. It is there that they discover that Lily is pregnant with Daisy Eriksen.