Okay so we all know Nightmare keeps a chicken named Kevin as a pet, but I love this headcanon too much not to share.
What if Nightmare was a HUGE animal lover. Like... he would always bring Kevin in the house when there's extreme weather cases in whatever AU they are in, always has the rooster eat a part of his dinner (like spaghetti), constantly swipes books about how to care for birds from JR's Librarby, and in anti-animal cruelty movements, even if most of JR is involved, would totally disguise himself and raise signs about the horrible conditions of battery cages/forced molting/high production units/etc.
Another thing would be if Dream was an extremely heartless jerk (which he isn't... most of the time), and he wanted to kill Nightmare's chicken...
Nightmare would literally fight to the death to protect Kevin.
Bonus brownie points if Kevin comforts Nightmare to the best of his abilities when Nightmare's down, (If NM's human) would preen his hair, perch on Nightmare's hand everytime the command was given, fly on top Error or Cross whenever Nightmare was loosing in a PvP game, and be Nightmare's alarm clock at four in the morning.
