Belevedere's sexuality
First, I am talking about the character of Lynn Belvedere, not Christopher Hewitt the actor or his lifestyle.
I noticed that around the middle of season 3, Mr. Belvedere's sexual nature sort of changes. In the early seasons he is largely asexual. The episode from season 2 where he dates Wesley's teacher is pretty lackluster with no real sparks. And there is an episode called 'The Auction' where a woman holds him captive in her house and tries to get romantic with him, but he is not at all turned on by that.
I think when Liz Sage joins the show as a producer and writer in season 3, that's when he changes. The first episode I notice the change is the one where Wesley gets blamed for Kevin taking a girl up to George and Marsha's room. Belvedere has a fantasy involving the young woman. Then in a season four episode called 'Kevin Nightingale,' he has a swarm of sexy female nurses around him. And in part two of 'The Trip,' he has a throng of scantily clad ladies around him at the house when everyone but Kevin is away.
So he becomes a lot more outwardly heterosexual as the show moves forward. I think this was an improvement in his characterization.