Id like to think Altman (24 at the time) wrote that Mike Carter listening to the Exposition Lady on the Many Records scene himself (it slaps, especially the bit where the woman talks to the person listening in), plus that amusing set piece at the eye doctor's office.
Bodyguard is somewhat Meat and Potatoes 'Some-Mug-Set-Me-Up-Ill-Find-Out-Who-Can't-Go-To-the-Cops-Whaddaya-Crazy piece of pulp, elevated by some decent if occasionally uncanny direction from Fleischer (watch for those EXTREME close-ups and quick zoom-ins - say, maybe this did influence Altman after all) and in particular Tierney, who plays this ex-homicide detective turned bodyguard turned Man Solving His Own Frame-Job with some quick skills, a bit of wit and a number of swift punches and choke-holds (not to mention disguises, re that Eye doctor scene). Everyone else here is more or less serviceable, but his presence single-handedly makes it compelling; in another world, he couldve been a more hard-boiled Dick Tracy.
I'm not sure if it would be quite as memorable without its star and a few above average twists (and one I called halfway through... Yeah, I wasn't quick on the draw this time). A true blue B movie that goes by like reading a crumpled paperback on a commute.
(Really, much as I kid, the Altman part is a bit of a foot-note, one of four credited writers, and he didn't go back to movies gor another nine years)