I'm gonna screw this up cause I heard it second hand:
Homer: Hey marge look at the BBBQ I just bought
Marge: What does that extra B stand for?
Homer: BYOBB
Marge: And that extra B?
Homer: Oh that's a typo.
The episode also has the infamous: "You don't win friends with salad" song.
I think it's:
Homer: Hey kids! I just got my barbeque invitations back from the printer!
Lisa (reading): "Come to Homer's BBBQ. The extra "B" is for BYOBB."
Bart: What's that extra "B" for?
Homer: That's a typo.
thanks!