What's one celebrity impression when you can do 29 in less than four minutes — while singing, no less? That's exactly what singer-songwriter Rob Cantor seemed to do in his latest video, but in a newly released behind-the-scenes clip, we learn the truth: Rob had the help of 11 impressionists. As for Rob, he admits, "I cannot do a single celebrity impression." To create the viral video, the impressionists recorded themselves singing Rob's original song called "Perfect," with the group covering everyone from Britney Spears  to Adam Sandler  to Gwen Stefani . Watch his lip-sync performance in the original video above, then watch the making of the video below.