Kayvan Novak turns up playing a bomb disposal expert.
The Other Darrin: Doug Whitney is played by Spike Jonze in the first two seasons and Jack McBrayer in the third. Unlike most cases, it was commented on in the season premiere.
The Other Marty: Dave was originally played by Russell Tovey in the pilot, but wasn't available when the series went into production. He was replaced by Blake Harrison, and all of Dave's scenes had to be reshot.
Viral Marketing: To promote the series, IFC created a fake website for Thunder Muscle. The URL is now defunct, but the site has been archived here.