The photograph that Raj has on his office wall behind his chair, the one with the two orange rings, is the Hourglass Planetary Nebula taken in 1995 by the Hubble Space Telescope.
Sheldon's T-shirt in the opening represents 1950s "The Flash" getting his power. Barry Allen was covered in chemicals (first symbol) after a shelf of them was hit by lightning (second symbol) which resulted in his becoming "The Flash" (third symbol). Thus: Chemicals Plus Lightning Equals the Flash.
Sheldon mentions that he wants to bring back the canceled show Alphas (2011) and this fact is used for humor. Ryan Cartwright, who played Gary in Alphas, appeared in The 43 Peculiarity (2012) as Penny's classmate Cole.
Sheldon references the eventual fate of 3 cult TV shows, mentioning that Buffy the Vampire Slayer (1997) "continued on as a comic book", Firefly (2002) did a movie (Serenity (2005)) "to wrap things up", and that Heroes (2006) "gradually lowered the quality season by season till we were grateful it ended."
The title refers to Amy helping Sheldon work on his compulsion for finishing things or his closure about various activities.