Billy Gardell was deeply in debt and tired of scrabbling for parts that would get cut or recast. He turned down the role of Mike and was preparing to move his family back to Pittsburgh, where he'd lined up a job at a local radio station, when Chuck Lorre called and said that he would personally fight the network to keep Gardell as Mike because he believed that Gardell was the only person who could play the role and asked Gardell to trust him. Gardell did, Lorre kept his promise, and the show became a hit.
From the second episode:
Mike: Let's see, when I picked her up she was loaded on codine and singing at the top of her lungs... Carl: So far, so good. Mike: She then proceeded to drink an entire bottle of very expensive wine, after which she yanked the hair out of my nose, started a fight with the waiter, and then passed out on the crapper... Carl: ...That doesn't sound so good. Mike: It wasn't, Carl! It was a total disaster! Carl: I'm sorry... I guess you'll never see her again. Mike: Are you kidding? I'm gonna marry that girl.
Mikes relationship with Carl's grandmother. She regularly comforts him and gives him sage advice, and he affectionately refers to her as "Nana".
Victoria's dedication to her job. Yes, she applies makeup on corpses but she does it so that the dead can leave the world in dignity.
Mike proposes. Molly says yes.
And then there's the whole wedding.
The cold open of the episode "Molly in the Middle" in it's entirety is a combination of this and Moment of Funny, in which Mike and Molly discuss the possibility of having a baby. The way they work off each other in the conversation, you 100% buy they are an incredibly adorable recently-married couple.
The biggest supporter of Mike and Molly having a baby? Vince. He actively encourages them the whole way because he can't wait to be a Grampa.
When Mike reads Molly's second book, the story of Peggy's life, and it brings him to tears.
Where are you going?
I'm going to go hug my mom!
Peggy admitting that for all the things that have gone wrong in her life, the one and most important thing she got right was Mike.
Peggy's reaction to finding out she's gonna be a grandma. She drops her usual cold facade and immediately glomps Mike and Molly, screaming in joy.
Vince and Victoria's reactions to Mike and Molly adopting a baby is adorable. They're literally singing about how they're going to be a Grampa and an aunt respectively.