From Muppet Wiki

Alex Trebek has been the host of the popular trivia game show Jeopardy! since 1984. He appeared with some of the cast of Sesame Street on his show on April 4, 2006.

Big Bird, Elmo, Rosita, Oscar and a dozen Muppet Eggs appeared with Trebek to help promote Sesame Street’s Season 36 theme, "Healthy Habits for Life." Trebek then appeared on Sesame Street itself in Season 37.