Credits Gag: There are a couple, mostly in the juxtaposition of assorted credits with images from the film. The best of these is that the Costume Designer's credit appears with an image of the naked Holmes tied to a bed.
Deleted Scene: So, Irene never got around to trying to stab Holmes with a hair pin or kneeing him in the... meerschaum, eh?
Dyeing for Your Art: Downey did this movie in between the first two Iron Man movies. Look at how beefy Tony Stark is compared to how wire-thin Holmes is. That takes dedication.
Rob also was meticulous in making sure his accent was perfect for the character and historical period. As per Guy Ritchie's interview on Top Gear, he succeeded.
It was perfect for modern perceptions, but it wasn't historically accurate. Historical British sounded much closer to modern Americans than modern Britons. It mainly revolves around rhotic speech.
Hey, It's That Guy!: Both Peter Cushing and Christopher Lee have portrayed the great detective with great acclaim in two separate occasions. Peter Cushing in particular has been considered amongst the best out of the more than 75 actors to have portrayed the character, which include the likes of Jeremy Brett, Basil Rathbone and Vasily Livanov, and was known to have an encyclopedic amount of Holmesian knowledge.
Real-Life Relative: In the Granada TV series, after a fashion. In the adaptation of The Problem of Thor Bridge, the role of Neil Gibson is played by Daniel Massey, whose sister actress Anna Massey had been married to Holmes actor Jeremy Brett from 1958 to 1962. Although the couple had divorced, due to Brett's bisexuality, the split had been amicable, and the two had remained friends.