I saw the one where Brian comes out dressed as a banana & is singing Peanut butter jelly & it made me roll laughing.
Brian is trying to cheer peter up in the episode & he puts on a banana costume & starts singing Its Petnut Butter Jelly time!!!
Brian is trying to cheer peter up in the episode & he puts on a banana costume & starts singing Its Penut Butter Jelly time!!!

It's episode 66 called The Courtship of Stewies Father.

Peter: Aww things were going so good for me and Stewie, but now he hates me again. Brian what should I do to win him back?
Brian: That depends. Do you want my advice or are you just asking random questions again?
Peter: What's a hypotenuse?

You can watch that clip any some other really great ones here. http://www.milkandcookies.com/keywords/familyguy

I saw it, and it was hysterical, but I don't remember which episode it was from. peanut butter, jelly. peanut butter, jell. peanut butter, jelly with a baseball bat. Get on adult swim's website, www.adultswim.com, and search their forum. someone there is bound to know which episode it was.

I laughed for ages after seeing this part.