The working title for the episode was "Marshall Forgets His Pants."

(Talking about Ted's ex-girlfriend Karen)
Ted: Would it be the worst thing in the world if I gave her a call?
Marshall: No, Ted, it wouldn't be te worst thing in the world, it would be the fourth worst thing. Number one: Supervolcano. Number two: An anteroid hits the earth. Number three: All footage of Evel Knievel is lost. Number four: Ted calls Karen. Number five: Lily gets eaten by a shark.
Lily: I'm Lily, and I approve the order of that list.

Barney: A hug is just like a public dry hump.
Marshall: I think you're hugging wrong.

When Ted asked why Lily had to paint Marshall nude, she said it was because he ate her bowl of fruit. However, in episode 2x13 "Columns" we learn that Lily she painted Marshall nude because she wanted to do a nude study for her art class, but Marshall wouldn't let her see any other men naked.

When Karen walks in and sees Marshall naked, he is holding a flower. Then the shot zooms in on Karen, and when it zooms back out, the flower is gone. (In the finished portrait, which we saw in episode 2x13 "Columns", Marshall is holding the flower.)

When Marshall stands up and reveals that he is still wearing the cut-off pants, he says that it's because they show off his calves. We learn in episode 2x03 "Brunch" that Lily is turned on by Marshall's calves.