MORRRRT<3 I wanna give him alllll the love~ Bahaha, WELL, Rodeo is probably freaked out by Mort's ability to NOT DIE. He'd totally think he's probably a zombie or a vampire or something and in Mort's presence would pull up the collar of his shirt and possibly clutch a crucifix to his chest if one is nearby.
Lucky will think that Mort not being able to die is very sad, since to him knowing there's an end to life is very comforting. I'm sure if he ever spoke to him, he'd tell him as much, because sometimes he doesn't know that it's impolite to say certain things. Homeschooled kid problems.
Prince would have a grand old time with Mort, and I have a feeling that he DELIGHTS in using Mort to get free things when he can convince Mort to play along. "NO I WILL NOT PAY FOR THIS SANDWICH, MY FRIEND GOT IMPALED BY YOUR BUTTER KNIFE." He'd definitely try to inspire the worst in Mort and try to get up to lots of trouble with him <3