Quark's comment to Odo in the episode about people's suspicion of Odo and Changelings is one of Armin Shimerman's three speeches in the show that he is most proud of for what it had to say.
J.G. Hertzler guest stars as the changeling Laas in this episode. Because he regularly plays Klingon General Martok, he was credited in this episode as Garman Hertzler to mask the fact that he was playing a different role.
J.G. Hertzler based his performance on William Shatner. He wanted Laas to be annoyingly judgmental, as if humanoids are beneath him, and that all they do is upset the natural balance of things. Shatner has that way of taking extended pauses and over enunciation. That could work for Laas. He described it as "Laas doing William Shatner doing Kirk!"
Andrew Robinson, who played the recurring role of Garak, was considered for the role of Laas. Both roles required heavy make-up but the staff felt that Robinson's voice was too recognizable.
The title of the episode is a reference from Greek mythology. The Chimera was the daughter of Typhon and Echidna, and sister to Cerberus and the Hydra. Legend says that she had three heads; the head of a lion, the head of a dragon, and the head of a goat (which could breathe fire). Obviously, the relevance for the episode is to be found in Laas's ability to be anything; similarly, Chimera was no one thing. Interestingly, Chimera was ultimately slain by Bellerophon, riding on the winged horse Pegasus. The very next episode that went into production after "Chimera", "Inter Arma Enim Silent Leges", features the USS Bellerophon.