Elijah C. Skuggs: Styrofoam cup.
Ortiz the Dog Boy: Twelve milkmen is theoretically possible. Thirteen is silly. Looks like there's one milkman too many, Coogan.
Elijah C. Skuggs: A lot of milkmen on the same route. No wonder they fight.
The Eternal Flame: Fire in the hole.
Eye: Dat sock fulla holes, mon.
Answer: Honestly, I think it was just a bit of fun for Reeves. It's really not uncommon for prominent actors to do uncredited roles and cameos in films. I've seen it happen before many times. And given that the director/co-writer/co-producer is his "Bill and Ted" co-star Alex Winter, I have serious doubts they were worried about any "Bill and Ted" association. (If anything that would have helped them at the box office.) It was probably a case of Reeves doing it as a favor for a friend, and they decided to have fun with it and keep him uncredited to see if anyone would figure it out.
TedStixon