The late Ricardo Montalban was a guest star on both seasons of Freakazoid! as the Khan-like villain Guitierrez. Paul Rugg, writer and voice of Freakazoid, shares his memories of how Montalban got cast and how much fun he was to work with. Read the whole thing, but here's an excerpt, followed by the "bloopers" scene he describes.
Perhaps my fondest memory was when he had to come and do addition dialogue for the episode HERO BOY. For reasons we couldn't figure out...the episode came up about 3 minutes short. So, John and I devised a solution in which Guitierrez would show Freakazoid his favorite bloopers. Our editor found some of the dumbest, old, live action black&white footage I've ever seen. We cut it together and I wrote some dialogue to cover the footage. When Ricardo arrived he had neither seen the footage nor his dialogue. I explained the setup to him. "Guitierrez is crazy about these bloopers and he really thinks they are funny and he really wants to show them to Freakazoid and..."
"Ahhh, yes. I see. I see. Yes. Let's do it." Ricardo and I went into the booth. We ran the footage and he made me laugh so much that I didn't do my lines. The sound guys were rolling. Andrea was in hysterics. Bruce Timm popped his head into the room and started laughing.