Revealing mistake: In some of the shots where Greg is in the pool with no swimsuit on, you can see that he is wearing shorts in it before he asks the girl to give his swimsuit.
Revealing mistake: When Frank is unplugging the power cables from the T.V. He says "I will, I can, I am" you can see Greg mouthing those exact words at the exact same time. (00:16:50)
Answer: It is used after Greg tells Rodrick that Heather has accepted loded diper.