I'm loving these headcanons. How about Shrek (and Donkey and Fiona, for that matter)?
You got it!
Shrek:
-Despite being friends with Puss in Boots, Shrek is actually a dog person. He's resolved to never tell Puss about this, knowing how Puss will be so incredibly offended.
-He's good friends with Knuckles the Echidna from the Sonic the Hedgehog franchise. The two keep in touch via packages because both REFUSE to touch a computer (and both of their handwriting sucks too much to write letters to each other).
Donkey:
-Donkey HATES and fears animatronics. He freaks out at the very sight of them and has accidentally destroyed a few in panic (Don't ever introduce him to the FNAF crew).
-Donkey is THE most hygienic of the Shrek crew. The minute he catches a whiff of someone smelling even slightly off? He is INSTANTLY getting them to go back into the bathroom and do their hygiene for god's sake! He will WATCH them like a hawk if he has to just to make sure.
Fiona:
-Fiona owns and keeps several lockets. She mainly uses them as ways to chronicle the journey she and her cast-mates have been through over the years.
-Fiona has a fondness for Jenga and other stacking games. She's really good at them as well.
