Wil Wheaton's address numbers shown on his house when Howard and Sheldon go to see him is 1701 which is the number of the Enterprise on Star Trek: The Next Generation (1987).
Title reference: Leonard struggles to find out which woman in his life correlates with a certain character in his novel.
All of the main actors (except Jim Parsons and Mayim Bialik who play Sheldon and Amy) plus Christine Baranski (Beverly) get to play a different character in this episode; Wil Wheaton probably doesn't count, since he is still Wil Wheaton playing Professor Proton.
The name of the protagonist of Leonard's novel, Logan Dean, may have been inspired by the Marvel Comics characters James 'Logan' Howlett (Wolverine from the X-Men) and Karolina Dean (Lucy in the Sky from Runaways). The TV adaptation Runaways (2017) had actually just started airing on internet 2.5 months before this episode was broadcast, so it may have been fresh on Leonard's mind.
Amy says that she has an oily scalp. She had a dry scalp in The Robotic Manipulation (2010) for which she used dandruff shampoo, so apparently it worked too well.