- Acting for Two: James Nesbitt pulls it off, with Tom and Mr. Hyde seeming like two extremely different people. He's helped by some quite extensive make-up, which is so subtle and complements the acting so well, you might not even realize it's there. He also plays the original Dr. Jekyll and his Mr. Hyde in flashbacks and photos, since Identical Grandson is in play.
- Fake American: Benjamin Maddox, shadowy agent and possessor of an absurd accent that sounds like North Dakota by way of the bayou.
- Hey, It's That Guy!:
- Reality Subtext: The actress who played one of the lesbians became unexpectedly pregnant between signing on and filming, so Moffat just rewrote it into the script. He later said that if anyone could have known that the actress' baby bump wouldn't be prominent (which can vary from pregnancy to pregnancy even for the same woman) the production staff just would have been able to work around it without re-writing.