The Big Bang Theory Season 3 Episode 6
The Cornhusker Vortex
When Leonard and the boys head out for a kite fight, he runs into Penny who tells him she's having a football party with some friends over. She didn't invite Leonard because he would get bored, but Leonard is convinced she's embarassed to introduce him to her friends. He has Sheldon of all people teach him football and he attempts to watch the game with them next week.
At Penny's, Leonard ends up just repeating rules more so that actually watching the game and getting weird looks from the guy. When Sheldon comes over to ask Leonard to fly kites, Penny gladly sends him off. When he leaves the room, she doesn't necessarily make fun of him, just says that's my boyfriend... he's really smart. Definitely still embarassed of her little man that flies kites, but not ready to insult him when he leaves the room. Good.
Meanwhile, Raj gets upset at Wolowitz when he ditches him during a key moment during the kite fight to hit on a girl he has no chance with. Wolowitz tries to win back Raj by taking him on a bromance date to the tar pits, but ends up getting ditched again by Wolowitz to chase after a girl he has no chance with... but this time with Raj's blessing.
The episode title, "The Cornhusker Vortex," comes from the team, the Nebraska Cornhuskers, that Penny and friends watch.