When Peter goes back in time and messes things up with Lois, she ends up marrying Quagmire and having a Chris, Meg and Stewie that look like Quagmire instead.
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Family Guy Season 5 Episode 18 Quotes

(Lois walks out of Quagmire's house to pick up a letter from the mailbox)
Peter: Lois, what the hell? I'm gone for one night and you sleep with Quagmire?!
Lois: Mr. Griffin, what I do with my husband is none of your business.
Peter: Husband?
Quagmire: Morning, Pete. Hope you and Molly can still join us for dinner tonight. Baby, Let's go play "Schoolgirl & Guy Who Has Sex With Schoolgirl".
(Lois giggles)

Lois: Peter used to be so passionate, but now he doesn't seem to be interested in me.
Quagmire: Lois, if I may, Peter doesn't you. As a friend, I think you deserve to be with someone who knows how to be a gentleman.
Lois: Oh, Glen. You're so sweet. (They embrace) Something's poking me.
Quagmire: It's alright. It's just my wang.