The Arrival - S1-E4
Trivia: Michael Cerveris makes his first significant appearance in this episode as The Observer/Bald Man. However if you watch the series from the beginning, he makes fleeting appearances in every episode, sometimes on a tv screen.
Trivia: Cameron meets a prototype robot that smiles and waves at her in in the exhibition outside the chess tournament. Briefly visible on its control screen, alongside basic commands, is the word "BladeRunner", a reference to the classic sci-fi film which also features a dystopian future populated by humanoid robots.
Clone Cadets - S3-E1
Trivia: Commander Colt watches Domino Squad do their test and says, "Start The Citadel challenge, version THX, variable 1138," which is a reference to THX 1138, another film by George Lucas.
Trivia: Was originally meant to be shot entirely with web-cams, with the characters reflecting on the events through dialog in video-blogs. However, after the story grew bigger during the writing process, it was ultimately decided that it would be filmed like a more traditional film or series, and the video-blogs became more of an occasional recurring motif than a main focus.
The Scorn of the Star Sapphire! - S3-E5
Trivia: After freeing Miss Taylor from the grip of Star Sapphire, Green Lantern encases her in a green energy box and flies her away. The box is shaped almost exactly like a shuttle craft from Star Trek. (00:15:50)