This is the third time in which Mayim Bialik's broken right hand from a real-life accident had to be hidden. When Penny is taunting Sheldon about losing Pictionary and Leonard points out it's a well-rounded game, Amy can be seen placing the box on the table, revealing her right hand laying weirdly dead on the couch, one finger is jarred in a way that makes it look like it's made of rubber.
During the pie eating contest scene, as Amy (Mayim Bialik) is counting down, Penny (Kaley Cuoco) looks directly into the camera with a clearly uncomfortable expression just moments before putting her face into the blueberry pie.
Sheldon is wearing a "73" shirt. In season 4, he mentions that 73 is the best number. Coincidentally, Jim Parsons was born in 1973.
Title reference: the impact of Howard's grand return to Earth is severely lessened by his friends.
In the opening teaser, when Stuart says he can give Sheldon 30% off comics, you can see Jim Parsons smile and break character