She takes him to a gay bar.

Of course she takes him to a gay bar; there is no world in which she does not take him to a gay bar.

"Yeah, I think she might have been going for Sheldon, but he has fantastic dodging reflexes, so... Amy was the weaker antelope. It's the way of nature, Leonard; she is red in tooth and claw."

"I don't think it's from the buildings," Sheldon said. His voice sounded flat and dead, and it startled her so much she jammed on the brakes. Hysterical Sheldon she could handle. Blowing everything out of proportion, no problem. But defeated, lifeless, dead-sounding Sheldon threw shivers up and down her spine and an icy pressure into her stomach. "Sheldon?"

They go inside, and Penny almost forgets about the van. This is her first mistake.

It comes as something of a shock when she throws the shoe at his head.

"You turned your girlfriend into a slash fan!" Howard hissed. "It's bad enough that your mother thinks I'm gay, now Penny is going to be giving me the 'thumbs up on your alternative lifestyle' every time I go near Raj!"

Howard looks over at Sheldon, who is placidly watching them. "Could we have some privacy here?" he snaps. "This is kind of a personal conversation."   "Well, excuse me for having the temerity to be in my own apartment," Sheldon says. "By the way, that was sarcasm," he adds before retreating back to his bedroom.

"Au contraire, Penny, it is the thrill of watching the math play out that excites me."