In Bart to the Future, he is visiting Lisa and they are having a conversation while at the White House. She sends him on mission for him and his friends to go to Camp David so that they can work on report focusing on "coolness". Before he leaves the White House, he asks her if they can skinny dip while there. The conversation ends with her agreeing to that and saying that pants couldn't be kept on Kissinger.
This is the conversation that they were having.
Lisa: You know something, Bart, you're right. My lack of coolness is really holding America back.
Bart: Thank you. Down low! [extends his hand, but retracts it when Lisa tries to slap it] Too slow!
Lisa: [laughs weakly] You're too much, Bart. That's why I'm appointing you, "Secretary of Keeping It Real."
Bart: Wow? You're really asking for my help?
Lisa: Absolutely. I want you and your pals to go away to Camp David and write up a report on coolness.[escorts Bart to the door]
Bart: Well, if my country needs me ... can we skinny dip?
Lisa: At Camp David? Sure. They couldn't keep pants on Kissinger.
I know this may sound trivial because it's a cartoon and the episode was aired over 20 years ago but just out of curiosity,...What did Lisa mean when she said "They couldn't keep pants on Kissinger." to Bart?