Percy and Jason were standing side-by-side and listening to Piper talk about something, and Jason had his arms crossed. Immediately, Percy got sidetracked.

Piper noticed Percy staring at Jason's arms, while Jason was just listening to Piper, entirely oblivious. Eventually, Piper decided to speak up about it.

Piper: "Percy, are you checking out Jason's biceps?"

Percy, without even a shred of shame or embarrassment, smirked.

Percy: "Yes."

Jason just glanced at Percy, visibly surprised.