I literally signed up for an account to share this theory of mine, based largely on the fact that I saw both of these movies in the last month or so.
The Boyfriend School (1990) is a prequel to "Three Men and a Baby, (1987). It shows how Steve Gutenberg's character Gus becomes Mike, one of the titular bachelors living in the oddly fancy New York City apartment.
Evidence:
1. He is a cartoonist in both. So Gus was a moderately successful cartoonist in some random local town. He does newspaper comics, and is apparently good enough to afford a weird boat/house/thing, a Harley, and so on. In 3 Men, Michael is a cartoonist, with at least one breakout character, a weird cat looking thing who is never really explored or explained. He is obviously successful, living on the upper West Side of NYC in a palatial apartment with fancy friends and so on. He also sketches constantly, drawing the mural on the wall of the apartment's... Lobby? Foyer? Again, never explained.
2. New York City connection. In the Boyfriend School, Gus said it was always his dream to go there and be a big success, the American artist dream etc. Emily is even worried about him leaving for the city at the end of the film, though there's the Big Fake Out and he says he will stay. After the Emily thing goes terribly...because OF COURSE IT DOES, he decides to follow his dream and move out of his weird industrial shack and on to NYC.
3. The name. In New York, Gus Kubicek becomes Mike Kellam, the charming cartoonist who tries constantly to meet and talk to women, with varying levels of success. How hard would it have been for Gus to pick "Mike" as his new name?
4. Age. In 3 Men and a Baby, the three bachelors are clearly a little on the older side, celebrating Tom Selleck's 30th? 40th? birthday at the beginning. There are frequent references to their married friends, life changes, discontented girlfriends and so on. If Gus spent as long as he did feeling like a loser, and with the clear dismal ending of his Emily relationship, of Course he was looking to play the field a long as possible.
5. Family. Of the three bachelors in 3 men, Gutenberg is the only one who never mentions an extended family of any kind. The other two call their mothers, but not Gute. Possibly because his sister is a legitimate crazy person, who once convinced him to grow a mullet and use an absurd accent to woo a woman he had met once. Shelley Long's character is the worst person in Boyfriend School, and Gus/Mike has clearly cut her weird fish-hanging ass out of his life.
In theory, this could show that there's a large shared universe of Steve Gutenberg movies - a GuteVerse, if you will. That, or it's all a coincidence that I only noticed because I've been stuck inside the house for the better part of three months.
