I loved this movie as a kid and just watched it again yesterday after not having seen it in probably 20 years. I realized that Michael McKean who played Andy (Daryl's adopted father) was the same actor who played Lenny on Laverne and Shirley. For years, I had seen McKean play the silly and crazy Lenny and it was really cool to see him play a "civilized" and responsible adult, husband and father. Shows what a good actor he is. Nothing against the character Lenny just interesting to see the differences.
Michael has done a lot of really great stuff over the years.
Along with what you mentioned, you can't forget all of the amazing films he's done with Christopher Guest and the gang (Spinal Tap, Best in Show, A Mighty Wind), his spot on the SNL cast, and a lot more.
This is one of the best though, as you get to see what actual talent as an actor he has, when he can't "fall on a crutch" as he could in most of the types of characters that he has played.
I haven't seen this movie in a few years but Michael's performance was my favorite part. In the scenes were Daryl is taken away the sadness on Michael's face was haunting.
He was really great in this and also Clue from that same year. Another good one is the sleazy FBI agent Morris Fletcher on The X-Files. He's played so many different parts over the years that I've never really thought of him as Lenny. When you really think about it, he's pretty underrated as an actor.
I have always loved Michael as an actor. He also did a small part as a cop in Planes Tranes and automobiles. He also had a big part as the Brady's jerk of a neighbor in the Brady Bunch Movie. And lets not forget his great performance as Perry White in Smallville TV series. Speaking of which, he also happens to be married to Anette O Toole who played Martha Kent in Smallvile as well.
I wish he was able to do more parts like this or more male leads but he transitioned into character actor parts quickly, soon after the mid 80's. He was a natural comic but also an unsuspecting lead who could sway you. Not the greatest actor but he had that certain something, yes.