They were classmates at a posh L.A. high school – and Mary-Kate Olsen doesn't have fond memories of Spencer Pratt.
"He does not have a good temper," Olsen, 22, told David Letterman, during an appearance to promote her film The Wackness. (She makes out with Sir Ben Kingsley in the flick.) "He used to play on the soccer team ... (and) he walked out of a few games. He would walk off the field."
When Letterman pressed her for more stories on The Hills's 24-year-old villain (whom Letterman called "wormy" and "oily"), Olsen just giggled and said, "The Wackness is a great film!"
As for the rest of young Hollywood, Olsen simply advised: "Wear underwear! Wear your panties."
JOSH & FERGIE: ROCKED BY SCANDAL
Did he cheat with a stripper?
Married less than a year, the couple denies an Atlanta woman’s claims that she and Josh had a fling
Note that this week’s cover of PEOPLE may differ regionally
