On the Soupy Sales show in the 1950s and 1960s, there was an ongoing gimmick where there'd be a knock at the door and Soupy would open it to reveal a surprise celebrity guest. The best part of the gag is that neither Soupy nor the audience knew who the celebrity would be. Once though, Soupy's crew played a great prank on him where a stripper was waiting behind the door. COOP found the video on YouTube. It's a real hoot. From Wikipedia:
One time during the Los Angeles years, as Sales was ending the show, when he opened the door he saw a topless dancer gyrating with a balloon. Viewers saw only the balloon, although a second, non-broadcasting camera captured the uncensored version, and Sales was forced to try to keep the show going without revealing the risque events backstage.
Link
UPDATE: YouTube yanked the video, but reader Matt Sanderson kindly points out that right now it's still viewable via Delutube. Link
