Quote from Lois in Flashback
Lois: You know, I wouldn't give up a single one of them. Hal: They're our boys. No one else can say that. They're our boys. [looks at pregnancy test] Negative. Lois: Uh, all that worry for nothing. A girl would have been nice, though. Hal: Are you kidding? We've got you outnumbered five to one now and we're still losing. [both chuckle then kiss] Lois: Boys, go to your room!