Over the course of three movies, the "Hangover" series has prided itself on shocking and gross-out moments -- photos from the Wolfpack's first forgotten night, Stu's casual encounter in Bangkok. In the franchise's final chapter, in theaters Thursday (May 23), one of the sickest moments is significantly more innocent than the examples from previous installments, but it packs a punch nonetheless.

In a cameo appearance, Oscar nominee Melissa McCarthy has an intimate moment with Zach Galifianakis' Alan in a Las Vegas pawn shop, and from there, things get real.

"I didn't know Melissa, and we had just met kind of met that day," Galifianakis said when MTV News spoke with him in Las Vegas. "Sometimes you get lucky enough to have clicked with another actor or actress, and we just, I don't know, felt like we had known each other for a long time. That helped."

The connection must have at least helped during the scene, which has Alan taking the lollipop from his mouth and seductively placing it into McCarthy's, in order to get the information he needs about the location of Mr. Chow.

Galifianakis' co-star, Bradley Cooper, agreed that McCarthy brought something special to the set.

"There's something about [McCarthy] and John Goodman especially," he said. "They come on set and bring an energy. It's amazing because there's a set structure and a set energy with the three of us, but Melissa would come on, and as an actress, she's just cool, unflappable energy. She set the tone actually. She really is a very powerful performer."

Check out everything we've got on "Hangover."