After being made a fool of on David Letterman (twice!), Spencer Pratt has decided to lash out at former classmate Mary-Kate Olsen.

Earlier this month, The Hills star made a guest appearance on the late night program and was put on the hot seat by the talk show host. (You can see that video here.) When Pratt claimed that he receives fees of $100,000 to appear at clubs, Letterman simply couldn’t hold back the laughter.

Fast forward to past Thursday when Mary-Kate Olsen was on the same show promoting her new movie, The Wackness. David asked if Olsen had gone to school with any of the young stars in the news today—and that’s when the subject of Spencer Pratt came up. (You can see this clip after the jump.)

Hoping to get some dirt on Pratt, Letterman quickly got the insults rolling. “What a little worm that guy is! Don’t you think he’s a little wormy?”

While it was clear Mary-Kate was holding a lot back, she did acknowledge that he was not much different in his early years. “He used to play on the soccer team for my high school. He does not have a good temper. He walked out of a few games. he would walk off the field. He was like ‘Me or the coach!’”

And even though Olsen did her best to switch the conversation’s focus (because we all know she could have spent hours talking about Pratt), Spencer couldn’t resist hurling insults through Us Weekly at his more successful classmate. “I don’t really get why she’d use my name to get press for her little indie film that no one’s going to see. She should probably focus more on not getting dressed in the dark than on me.”

He then added on the signature Pratt charm. “I know I’ve made it in Hollywood when a famous troll is talking about me on Letterman. I forgive her, though. She’s had to go through life as the less cute twin, which must be tough.”

Wow. I’m surprised he didn’t also say that Heidi Montag was doing a special prayer for Mary-Kate as well.