I am just now sitting down to watch Tuesday's episode of Warehouse 13...and both Kaylee (Jewel Staite) and Simon (Sean Maher) make guest appearances. Serenity and Firefly, the series that inspired it, are among my all-time favorites to watch on a rainy day when Ben's not home.
Firefly: a clip from one of the episodes. Major fun, if you ask me.
Serenity: the trailer. More of the awesome.