In The Focus Attenuation (2014), Amy went to Las Vegas, making Sheldon the last member of the gang to have never been there. In this episode, he finally makes it there.
This episode marks the reappearance of President Seibert (Joshua Malina) after The Rothman Disintegration (2012), a span of 149 episodes.
Raj shows concern that if Sheldon's experiment creates a black hole, it could destroy the entire Earth. In The Pork Chop Indeterminacy (2008), when Leonard voiced the concern of several physicists that the Large Hadron supercollider could create a black hole and swallow up the Earth, Raj simply brushed them off as "a bunch of cry babies" and "no guts, no glory, man."
Title reference: Sheldon is trying to raise money to conduct an experiment to prove his string theory research.