Mary-Kate Olsen's appearance on David Letterman last night wasn't notable for her "I'm so tired" excuse for being barely able to hold herself up, but that she threw old classmate Spencer Pratt under the bus. Mary-Kate says the duo went to high school together, and that Mr. Pratt's temper problem often meant he'd scream his way off the soccer field when he didn't get his way. Also, he's "oily." Insider stuff here folks!