‘The Big Bang Theory’ returned with plenty of laughs following last week’s heart-wrenching episode.

Penny, Sheldon and their unique relationship came into focus when the duo tried out an experiment designed to make people fall in love. They spend the evening in Penny’s apartment asking one another a series of questions designed to deepen their relationship before staring into one another’s eyes for four full minutes.

It starts out amusing enough at first, but pretty soon they both let their guards down. Penny acknowledges that she uses humor as a defense mechanism and Sheldon admits that he envies her and how at ease she is around people. It’s not the only big revelation; she even gets him to admit that it is his birthday! Once she expresses surprise that he’s a Pisces, he shuts her right down.

In the end, the two find themselves staring into one another’s eyes. Although they aren’t supposed to talk, they both acknowledge how creepy it is and begin to reminisce about the day they met eight years earlier.

Penny admits she does love him, which doesn’t surprise Sheldon, who refers to himself as warm and fuzzy. However, she’s quick to clear up that it’s the kind of love she’d feel for a younger brother and the two walk away with a deeper understanding of each other.

That’s far from the only surprise of the night.

Amy and Leonard spend the night with Raj and his girlfriend Emily, who has remained largely absent this season. Emily suggests they go to a dinner theater where they will be locked in a room with a zombie and given two hours to escape. Of course, the room of brainiacs solves the puzzle in just under six minutes, giving them plenty of time to plan a big surprise birthday party for Sheldon after his experiment wraps up.

Gone but not forgotten, Howard and Bernadette are still reeling from the loss of Mrs. Wolowitz. They spend the episode in the airport attempting to track down the luggage that holds the ashes of Mrs. Wolowitz. They struggle with an airline employee who does her best to track down the bags. Howard insists it’s important as those are the ashes of the only woman who ever loved him! After being met with an eye roll, he swears to his wife he meant first woman, not only.

Things take a serious turn after Howard confesses he told his mother he had been too busy to drive her to the airport before her trip. She’d asked him one favor before she died and he denied her. This prompts sweet and meek Bernadette to pop right out of her shell and tell the airline employee that she better find the ashes because one way or another, she and Howard won’t be leaving the airport without a dead woman.

As it turns out, that threat was just what the airline needed. Howard is reunited with his mother's ashes and he promises to never leave her again, prompting Bernadette to acknowledge that those ashes will definitely be making their way into her bedroom.