Be sure to watch The Big Bang Theory Season 8 Episode 21 online right here via TV Fanatic to join in on all the laughs with Sheldon, Leonard, and the rest of the gang.

Not only does this episode offer the opportunity to hear Sheldon's new renditions of children's songs as ways to teach science, but it also offers new pairings and important decisions for our favorite characters.

When Raj is approached by NASA to work on a new project, he asks the guys for help. He and Leonard end up working on the project together, but they have a tough time getting started. Why? And will they be successful? Watch The Big Bang Theory Season 8 Episode 21 online right now to see for yourself.

Meanwhile, Penny is still considering whether or not to move forward in her acting career, and she goes to Sheldon for advice. So what advice does he give her, and does she make the right decision? It turns out, she also learns something about herself in the process.

What are you waiting for? Watch The Big Bang Theory Season 8 Episode 21 online right here via TV Fanatic! We offer many different ways to watch.