(He) is just being crazy - Es sólo que está loco
I personally wouldn't call anyone crazy. I would just say they have a medical condition.
Bésame el trasero that's how u say you are crazy about me
loco
You can say "Estoy loco(a)".
¿Eres loco?
Me vuelves loco/a.
No estoy loco
Estamos locos
You say, "tortuga loca."
Translation: mono loco
no demente, desquisiado, son others ways to say crazy.
You could say "Sombrero loco".