Looking for a clip from a Steve Martin movie...

[hi_im_god]

he did that schtick as far back as "happy feet" skits on snl.

if you're sure it's a movie from the 80's, you have the choice of:

the jerk (79), pennies from heaven, dead men don't wear plaid, man with 2 brains, lonely guy, all of me, 3 amigos, little shop of horrors, roxanne, planes trains and automobiles, dirty rotten scoundrels, parenthood, and my blue heaven (90).

probably one of the first 7 if you're sure it's a movie you remember and not the skit.