Mirror Image - August 8, 1953 - S5-E22
Corrected entry: In Good Morning, Peoria (series 2, episode 6), when Sam is creating a makeshift aerial on the roof, Al starts glowing blue, as Sam does when he leaps. He says "Look Sam, I'm leaping." However, in this episode, Sam sees someone else leap. When Al appears, Sam excitedly tells him about it and asks Al if he goes all blue and charged with electricity when he leaps. Al responds by saying that he wouldn't know, as when Sam leaps he simply finds himself back in the imaging chamber. If Al has never seen this why would he have assumed he was leaping in an earlier show?
Correction: Sam's leaps would also affect the people at Project: Quantum Leap (as seen in "A Leap for Lisa"). As well as "Good morning, Peoria" where Al thinks he's leaping, in "Future Boy" Al sees Moe Stein begin to leap before his machine breaks (Al visibly reacts). One of Sam's leaps after these episodes has changed something at the Project so Al gets sent back before Sam leaps.