Mark Gatiss and Steven Moffat have often slipped Doctor Who references into Sherlock. Shilcott's wall is remarkably similar to how the Doctor decorated his office in "The Invasion of Time" (1978), when he temporarily became President of the Time Lords.

This one hurts. Whether it is intentional or not, Peter Parker's final lines to Tony (before being dusted out of existence) include the line, "I don't want to go." It's the same line that Doctor Who's 10th Doctor (played by David Tennant) delivers right before he regenerates into the 11th Doctor, played by Matt Smith. Tennant even referenced his famous final line when he appeared in the 50th anniversary episode, The Day of the Doctor.

I'm a big Doctor Who fan.