Just like Sylvester Stallone wasn’t the original choice to play John Rambo, Richard Crenna wasn’t the original choice to play Colonel Trautman either. That role originally went to Kirk Douglas and character posters were even (officially) drawn up.
The day before filming began, at the 11th hour. Douglas, in a bout of extreme chutzpah, showed up with a revised script. He had the ending completely changed. Said Sylvester Stallone earlier a couple of years back:
“The plan to include Kirk Douglas snowballed into something I never expected. He said to me: ‘Here’s what I want. At the very end of the movie I should kill you. The audience sees a cop car driving away and as it disappears into the fog a hand reaches up to the rear view mirror. The camera turns up and we see me. It turns up a bit higher and I’m wearing your headband'”.
When Douglas was advised in no uncertain terms that his suggestion was not going to happen, he abandoned the shoot, leaving them in the lurch with one day to go. And with one day to go, Richard Crenna was drafted in. His first line was “I made him”, but having just come off a TV show playing a gay doctor, he was told to ditch the gay overtures that were still hanging around from all the hours of being in unmanly character at the hospital.
As for who was to play Rambo? Quite a few, but funnily enough Burt Reynolds was on that list. And he invited Stallone over to his house to advise him to turn down this horrible movie, just like he did. As Stallone said once to Total Film:
“I was at Burt Reynolds’ house having dinner and he said to me ‘… even if the movie dies and you’re good in it, it doesn’t matter’. I said to him, ‘Burt, that’s about the worst piece of advice anyone has ever given me, but thanks anyway'”.