I love Don Lothario! He's been a significant character in a lot of my gameplay starting with TS1, TS2 and now TS4. The biggest role he's ever played is as the spouse to my Drifter founder, Ella McDonough. My avy is an image of them as adults. :) They had a daughter, Della, who ended up being one of my most beautiful ever born in-game Sims.
In prior saves he had a child with the founder of a Legacy I started not long after the game first came out. I never finished it though since I had an old toaster of a laptop at the time and the file ended up way too laggy to continue.
He also had a fling with my free-spirited Hippie, Sunshine Beam, that resulted in a Son, James Beam. James went on to be the spouse of Queenarella's Gen 3 heir, Temperance Brennan, as the winner of her Bachelor/Bachelorette Legacy Challenge. They had 5 children together.
Don was also best buds with my first astronaut in the game, Andrew Hudson. I featured them in a short story here on the forum for Grilled Cheese week a long time ago.
My photography Sim, Nayeli Washington, did a photoshoot with him and they later ended up in bed together. I guess the photos turned her on or something. :D They're an on again/off again kind of couple though. She's just moved to San Myshuno and wants to keep her options open.
He's been good friends with many, many of my Sims, both male and female, in purely platonic relationships too. Surprisingly, he hasn't been one of my 100 Baby Challenge baby Daddies, yet. You'd think he'd be the first one since he's so easy to get in bed, being the town bike and all. But nope. Maybe if I ever continue that challenge he will be a candidate.
In my custom template save I use to start all gameplay, the Calientes are gone, but Don still lives in their house along with Paolo Rocca and a few other bachelors of my own design. I've never paired him up with Bella in TS4 as lore suggests should happen. I have a rule in my game that breaking up married couples or having affairs with married Sims is forbidden. I know that's not realistic, but, meh. My game, my rules. :)
So that's what I've done with Don in my game so far, I'm sure he'll appear in many gameplay saves in the future as well. He's just so fun in his randy demeanor. Viva La Don! <3