You aren't somebody until you're on Sesame Street . Here, a cool and unexpected bunch of cameos.
The Backstreet Boys
At the height of their career in 2002, the group sings "One Small Voice" with the lost sixth Backstreet Boys member: Elmo.
C-3PO and R2D2
The Star Wars duo helps Big Bird out with his counting in 1980.
Seth Green
In 2004, Green appeared playing "Vinny," a delivery dude for the "Letter of the Month" club. Looks like the Sesame Street characters may have been into Pottery Barn at that time.
Source: muppet.wikia.com
Johnny Cash
Cash would appear on the show several times. Here he is in '92 singing "Don't Take Your Ones to Town," a modification of "Don't Take Your Guns to Town." Nice.