The purple t-shirt Sheldon wears bears the symbol of DC Comics' Star Sapphire Corp, the members of which wield power rings powered by Love, represented by the purple band of the emotional spectrum.
The scenario around Leonard and Penny's break up with Sheldon being "the child" is copied from That '70s Show (1998) episode Pinciotti vs. Forman (2001), where Donna and Eric broke up and Fez was their "child".