This episode is dedicated to Jim Fuller who died in September of 2013. Jim worked on a few episodes of It's Always Sunny in Philadelphia (2005) and was also an assistant director on the hit show Glee (2009).
This episode has a lab rat named "Armitage Shanks," which is the name of a common British manufacturer of bathroom fixtures and plumbing supplies.
The title, "Flowers for Charlie," is a reference to the science fiction short story and subsequent novel "Flowers for Algernon" by Daniel Keyes, upon which the premise is based. This story is told by a series of progress reports written by Charlie Gordon, the first human test subject for the surgery. A 1968 film adaptation of the book was titled "Charly".
Written by Game of Thrones showrunners David Benioff and D.B. Weiss.