Lucille Ball's second husband made a few minor appearances on Here's Lucy. Daughter Lucie Arnaz's husband at the time Philip Vandervort did as well.

I think Cox and Arquette had already done the first Scream movie together, but were not yet a couple when he appeared on Friends.

Michael McKean is currently starring opposite Bryan Cranston on Broadway in All the Way. McKean is J. Edgar Hoover to Cranston's LBJ.