20th Century Shorts from The Magic Authority. The Magic Experts...

A volunteer is called from the audience to assist. Two large silks are then shown, tied together and then tucked inside his waistband. You now announce that the silks will be pulled directly through his body.

After the big build up you stand behind the spectator and give the silks a tug. They don't penetrate his body but instantly there is a pair of mens jockey underwear tied between the silks. This is hilarious!