Where We Left Off: To everyone’s surprise, Howard and Bernadette became engaged, while Raj and Penny did the unthinkable and drunkenly slept together.

What's Next: Expect cosmic fallout from Raj and Penny's hook up, since Raj's betrayal is liable to fracture the group. We'll also see Howard and Bernadette struggling with wedding planning, and Leonard will have a long-distance relationship with Priya to contend with.

Season 5 premieres Thurs., Sept. 22, 8PM ET on CBS