In the first movie, after "Fester" nearly gives himself away, Gomez vents his frustrations by crashing his model trains. We see a shot from inside the train, which features a miniature living person who looks up from reading the newspaper to see Gomez laughing maniacally.
Also a Creator Cameo. That's director Barry Sonnenfeld.
Gomez is having something of a Heroic BSOD after being forced out of his home, sitting around all day watching television.
Morticia: Why don't we go for a drive? Get some air?
Hippie-Nanny: Children, as your new nanny, I know that we are all concerned about the environment. So, this morning, let's discuss how to prevent forest fires.
Wednesday: Prevent them? [lights a very large match]
Strict Nanny: All right children, I have had it up to here. Now you just answer one simple question; where is that baby?
Wednesday: Which part?
Maid-Nanny: [with a hand puppet] Hello kiddies, I'm Polly the Puppet. What shall we do today? I know! Let's all clean our rooms!
Wednesday: [pulls out a devil puppet] Hello Polly, I'll clean my room ... in exchange for your immortal soul. [devil puppet rubs hand together]
Wednesday. Nothing can stop her deadpan - and sometimes deadly - response to the smugness and faux happiness that surrounds her.
Until the bit in Family Values where she apparently breaks under the peer pressure of the camp and begins smiling... Good thing she was faking it. The reaction is the crowning bit, though.
Amanda Buckman: She's scaring me!
Morticia's first line in Values
Morticia: Marvelous news. I'm going to have a baby [Beat] Right now.
What about Raúl Juliá's phenomenally hammy performance at the police station in Values?
My name is Gomez Addams, and I have seen evil! [cut to grandma and the baby] I have seen horror! [cut to Lurch] I have seen the unholy maggots which feast in the dark recesses of the human soul! [Morticia: "They're at camp"] I have seen all this, but until today, I had never seen you!
Which is also a Hilarious in Hindsight moment, because the actor that played the police officer (some guy named Nathan Lane!) would play Gomez in the musical.