Doing It for the Art: The entire production. The President of an actual micronation agrees to let a bunch of Internet wackos make a film about the "invasion" of his country. After they come together (some from different continents) he lets one of them beat him up on film. In addition, LordKaT, who had an injury during production, kept filming his role to the best of his ability. To say nothing of Rob Walker, who was the camera operator for most of it, and suffered a pretty nasty fall on the very first day.
Enforced Method Acting: Film Brain tried to pull this prior to his Heel-Face Turn, so that it would look as if he had been really affected by the Nostalgia Critic killing Santa Christ, so he sat around trying to make himself cry. Only when they came to shoot the scene, his castmates began asking him if he was okay, since he never told them he was going to do this.
During the hotel scenes, there was a maintenance worker outside the window was referred to as Mexican Spider-Man (A. K. A. Mexican Batman) during Linkara's commentary. During the commentary, Obscurus Lupa said that there was a side-quest where she and Mexican Spider-Man build the fence from Part 2.
I Am Not Spock: A lot of people apparently thought that Linkara was switching into an Ensign Munro persona when he donned his Starfleet uniform; Lewis denied this on his Twitter, saying that it was just Linkara in a Starfleet uniform.
No Budget: What little money they had mostly seems to have gone to travel expenses.
Kevin Baugh has autographed Star Trek photos in his living room.
Also, in the commentary, Obscurus Lupa refers to "Rule of Funny" by name, and mentions that she is a troper.
Throw It In: There was much less Linkara/Insano Arch-Enemy-ness in the original script (as Kickassia was about the whole team, not just their fights) and Lewis improvised most of his lines about Linkara's annoyance with the bringing-Insano-out plan. According to Rob's commentary, he even put in the Base Breaker line about telling Critic to kill Insano, despite the fact that his apparent best friend is still in there.
Playing Against Type: Inverted with Film Brain. He has said in commentaries that in reality he is a lot closer to his Kickassia personality than his one in Bad Movie Beatdown.
Troubled Production: Not only did they only have four days to shoot, but nearly everyone got injured.
Viral Marketing: See Forced Meme. There was a push to get #kickassia attached to as many Twitter posts as possible, a dedicated Facebook group, and twibbons for profile pictures.
LordKaT was going to have a greater role but he ended up getting a badly twisted ankle during filming.
According to Doug's DVD commentary, during the revolt, he was thinking of having the Critic using superconductor electromagnetism again against the rebelling Channel Awesome gang only for it to run out of batteries. It's a real shame.