And the only reason he was brought in was because Doug wanted Colin to be in TBF. The joke was for the "No, I'm your father" bit for the part of the movie that ripped off Star Wars, Doug's plan was for Luke to be the Luke Skywalker character so that when they did the line, Colin would pop in and say it. Just for the one line, that was it. Luckily for Colin, he was smart enough to know how stupid this was, so he declined.
Imagine being a nepo baby and failing so hard, the best you could do was getting hired by Doug Walker, in the hopes that your father might do a stupid bit in one of his movies. No wonder he trooned out.