Acting for Two: Quite often, especially among actors playing villains. Notable examples include:
George Peppard playing Hannibal, and a mook that Hannibal in the episode "Judgement Day."
Jack Ging is not readily apparent until you've watched the show twice - he played single episode villains in two different episodes ("A Small And Deadly War" and "Bad Time On The Border") before taking on the role of recurring character General "Bull" Fullbright.
In an episode with a science fiction con, a guy in a original Galactica Cylon suit walks past "Face". In the episode in question, it's actually Hannibal in the costume. The Actor Allusion was all Dirk Benedict's idea. While filming at Universal Studios for the second season episode "Steel", Dirk spotted a park employee dressed as a Cylon, and decided he wanted to film a little nod to his days as Starbuck. The director told him it was a dumb idea, but let him do it anyway. So, they had the Cylon-clad actor stroll nonchalantly across the frame while Face was all "don't I know you?" Fortunately for Dirk, the scene ended up being quite funny and they kept it in the credits up to season 5.
There was also George Peppard's allusion to his role as Banacek, where he played a similar role, by having Hannibal spout even more off kilter words of wisdom in "The Big Squeeze".
Another one for Peppard. In the Episode "The Rabbit Who Ate Las Vegas", Amy mentions that it's a shame Hannibal's being chased by the military as he is "a terrific actor" after Hannibal goes to great lengths explaining how he'll play his "character". A reference to Peppard's infamously stringent adherence to method acting, even when playing unchallenging roles.
The Danza: The Mexican Spanish dub of the series changed the name of B.A. Baracus with Mario Baracus, who was named after his voice actor, Mario Sauret (who later voiced Majin Buu).
Germans Love David Hasselhoff: The show was more popular in Belgium than it was in the United States, and Dwight Schultz and Dirk Benedict are still going over there for interviews and conventions.
Harpo Does Something Funny: Dwight Schultz has said one of the scariest things during the filming was how blank the scripts would often be.
Also, the writers frequently would not write the tag and then would just say to the actors "just make something up," or told Dwight Schultz and Dirk Benedict to loosely write up a tag.
The Other Darrin: In the feature-length pilot episode, Face was played by Tim Dunigan. The role was recast after the pilot as Tim Dunigan was much taller than the rest of the cast and the producers felt after the fact that he was simply too young to play a Vietnam veteran (as Dunigan noted, the war ended when he was still in high school). Since Frank Lupo and Stephen J. Cannell had written the role with Dirk Benedict in mind (NBC hadn't wanted him - or George Peppard - initially), Dunigan's miscasting may have been on purpose...
Screwed by the Network: More like Actively Sabotaged by the Network. The show was considered politically incorrect (showing a positive view of Vietnam veterans, among other things) and its success completely unexpected; it was subjected to Invisible Advertising, the network officials and producers actually badmouthing the show to the press, it was made a 'bad move' to write for, so despite its popularity it eventually succumbed to cancellation.
Throw It In: An extremely frequent occurrence, if grudgingly. There was a heck of a lot of Improv going on by the actors and notably Dwight Schultz, and though the writers frequently got mad by how the actors would go off-script or ad-lib lines, they often (if grudgingly) agreed that it should be kept in.
Stillborn Franchise: While hardly a flop, the film only grossed $170 million on a $110 million budget. The cast and director expressed interest but ultimately concluded that it wasn't profitable enough to risk it.
John Singleton was originally set to direct when the project was at Universal.
Whilst only Dirk Benedict & Dwight Schultz took up the invitation, a cameo was also offered to Mr. T - he declined, with Mr. T saying in different interviews that it was because he felt the film was too violent or because he wanted to actually reprise his role of B.A. Baracus.