Howard’s toupee actually came off on TV at least once. In a Scott LeDoux fight against a house fighter, the house fighter won, while most thought Ledoux should have gotten the decision. LeDoux was POed, and started yelling at Cosell like "OK, Howard, you say you ‘tell it like it is.’ Tell them that this fight was fixed.’ (Not exact words, but the intent). LeDoux, still in the ring, then kicked at the house fighter, on the floor beside Cosell. In the scuffle, I think the house fighter accidentally hit the wire connecting Cosell’s headset, and off it came, taking the toupee with it.
There’s video of it out there if you want to look, but unfortunately, it was a wide angle shot, so he have to look closely to see the toupee come off.