I think the greatest moment was when the family was all in the court and the judge had just sentenced Peter to 24 months in prison.
"Oh no", Louis says, and all of the family members say "Oh no" oen after the other for i think 4 or 5 people.
Then (the random comedy element

Everyone stares at him coldly and the camera goes to the Kool-Aid guy and he's lookin around with shifty eyes all embarrased, and slowly backs out of the hole in the wall. It was the funniest stuff I had ever seen in my life. I even taped it.
To farther show how random the show is and how the element of "randomness" is so funny to me, in that same episode, Peter says "Remember waht happened to Scott Baio (who playes Chochi in the show Happy Days) when he tried to say 'she sells seashells by the seashore'?"
And then they flashback to a scene where a girl is sitting on a couch and he walks in to the room. She says, "Hey Chochi, what does your mom do for a living?" So, i'm sitting on my bed watching, thinking taht since it is a tongue twister he would mess up and get embarassed or SOMETHING to that effect... See, now here is where the randomness of the show really shines.
He replies, "Ah, she sells seashells by the...." and he gets cut off when a bear bursts through the wall of the room he is in and pounces on his chest, pinning him to the ground. and the bear is just standing over him, growling with like all the fangs and saliva showing and such. It was just so random I was tearing with laughter. God, I LOVE Family Guy.
Well, you're probably tired after reading this, so get revenge for your eyeballs and wasted time by making me read your favorite moments.