Guest starring on "Sesame Street" is a gig more coveted than hosting "Saturday Night Live." So meeting Elmo, Grover, Big Bird or, if you're really lucky, Snuffleupagus, isn't something just any celeb gets to do. Most recently, Ryan Reynolds joined the team, or rather the A Team, to help teach kids the importance of the letter A. (Cute, right?) In honor of the series' 41st birthday, we've rounded up some of our favorite celebs who can tell you how to get to Sesame Street.