I like to think that Enid and Wednesday call their daughter nicknames, but ones that contradict the other parents' nickname like
Shelley: mom's!
Wednesday: Yes, my dark cloud?
Enid: Yes, my rainbow?
......
Shelley: Look what I did!
Wednesday: Good job, my little scorpion.
Enid: OMG, great work, lil pup!
......
Shelley: Mommy?
Wednesday: Yes, my bundle of misery and pain
Enid: What is it, my little bundle of joy and sunshine?
.......
Shelley: Booo!👹
Wednesday: Good try, my little yara ma yha who, maybe you'll get me next time.
Enid: wow😨 you got me again, my little..... little...... Wednesday, what the hell is a yara ma yha who?
Wednesday: a small tree-dweller that hides in trees then drops onto it victim's as Shelley just did.
Enid:......I don't know how to counteract that, so I'm just going to agree with you this one time. You really got me again, our little yara ma yha who!