I was watching an interview with John Ritter on Conan in 1997 (https://www.youtube.com/watch?v=YODf8O4P1zU). At 2m00, John describes an incident on the set that was severe enough to knock him out.

Although he describes the moment, I can't figure out which episode he's talking about.

Ok, got it. S07E01, "A Night Not To Remember". https://www.youtube.com/watch?v=31Xb7W5_lqY at 6m16

I didn't know about that!