Lyric correction: I don't know how Lerner wrote it, but Marvin sings it
'Do you know where hell is?
Hell is in hello.
Heaven is goodbye forever, it's time for me to go.'

And another verse:
'Wheels were made for rollin'
Mules were made to pack,
I never seen a sight that didn't look better lookin' back.'

And separately, in Cat Ballou, Lee Marvin at one point punches the horse, and decks it.