I have been watching Friends for years. YEARS. I've seen The One With the Fake Monica dozens of times. Maybe a hundred. The only context I had for Joey Tribbiani's stage names in that episode is Joseph Stalin, so I'd always assumed Joey Heatherton and Holden McGroin were serial killers I'd never heard of (probably because I was pretty sure they weren't dictators and Joey says something about Stalin being a murderer). I figured since I was 10 when the episode aired the names were just a part of early nineties culture I wasn't familiar with.
I finally realized today Holden McGroin is a joke. A joke! That I totally didn't get for all these years!
Holden McGroin = Holdin' my groin
Mind = Blown
IQ = Questionable
As you were.
(P.S. I guess Joey Heatherton is an actress and singer. Sorry for assuming you were a serial killer, Joey!)