In the episode, "Fonzie the Father", Louisa, a pregnant wife of Fonzie's buddy, is told to stay with the Fonz until he finishes his cross-country race. Louisa shows up at Arnold's Drive-In and asks Potsie, Ralph, and Richie a question.
Louisa: Hi! Excuse me... which one of you is Richie?
(Potsie, Ralph, and Richie notices Louisa's baby bump, and points in the opposite direction.)
And after Richie is telling the Fonz that Louisa is looking for him, she shows up, taps him on the shoulder...
Louisa: Excuse me... Hi! I'm Louisa!
Fonzie: (looks at Louisa and notices she's pregnant) Hi! I'm Potsie Weber!
Fonzie shows up unannounced at Chachi's new job as a photographer's assistant... and flips out when the girl being photographed completely disrobes.
Photographer: So, how do you take a bath?
Fonzie: Without cameras, usually!
When Fonzie and Pinkie Tuscadero decide to get married, but don't make their intentions clear in front of a nun. It leads to this exchange:
Pinkie: Yeah, let's do it!
Nun: OVER MY DEAD BODY!!!
(The live audience loses it)
Fonzie (after the laughing dies down): We're talkin' about gettin' married!
On the 20th anniversary show they show some outtakes including one of Fonzie kissing Marion Cunningham's neck then making out with her, then another which shows her coming down from his apartment with a coy smile while she buttons up her blouse.
Another intentional gag was a take on a scene where Fonzie snaps his fingers and a crowd of girls is supposed to follow him offstage with their arms around him... only in this case it's a crowd of dudes instead.
The iconic moment when Fonzie goes to comb his hair in the mirror and realizes.. ayyy.. it's already perfect.
The 30th anniversary special spent half its running time with Garry Marshall hosting a cast reunion at the Arnold's set. Scott Baio took a seat at the far end.