Maybe his dad gives a small smile and a nod. He could be a bit reserved in his reactions but still show that he appreciates Adrien's attempt at humor. He might say something like 'That was quite clever, Adrien.'
Well, perhaps the fanfic is about a world where cats can talk and Adrien is sharing with his dad all the funny cat - related puns from this fictional world. For example, the cats might make puns about their favorite fish or the warm spots they like to nap in.
Since I don't know the specific content of this fanfic, it's hard to give a detailed summary. However, if we think about it, perhaps in the story Adrien uses cat puns to amuse his dad. It could start with Adrien seeing a cat and then coming up with a series of puns based on the cat's behavior or appearance. For example, if the cat has big eyes, he might say 'Dad, that cat has eyes like saucers, it's so meow - velous'.
The funniest part could be when Adrien makes a really cheesy cat pun that catches his dad off - guard. For example, if he says 'Dad, this cat is so cool, it's the cat's meow!' and his dad just bursts out laughing at how corny it is.
If Adrien were Hawkmoth in fanfic, it could change the dynamics of the story completely. It might explore his internal conflicts and the impact on his relationships with other characters.
Perhaps Adrien becomes Hawkmoth because he's been pushed to the edge by Ladybug's rejections. As Chat Noir, he's constantly in love with her but feels unappreciated. The pain of this unrequited love could twist his perception of good and evil. He might think that if he were in control as Hawkmoth, he could make Ladybug see him in a different light. He could use the power to create situations where Ladybug has to rely on him more, or at least understand his pain.