Sometimes people call friends or people who are smooth with ladies Don Juan.

That jon, he's such a don juan.

Person #1: "Dude, check out that Don Juan over there...He's totally killin' it with those chicks."

Person #2: "Oh yeah, thats Jacob."

The modern version of a Don Juan would be a pimp or a playa.

Ian: Dude, Mike's such a Don Juan~ -_-

This Guy was apparently a total Don Juan because every girl who spoke to him automatically tried to ask him out.

a guy and his girlfriend in conversation:

guy: Listen sweetie, Emily. I am a Martian, and therefore have to consider it my duty to warn you that at parties, my father can sometimes get carried away and become aDon Juan.

Emily (shrieking): What? Are you serious? As a Venusian, I would like to know how your mother would handle such a situation.

Carl: Well. I don't get on that well with my dad anyways, and, besides you are welcome to ask my old lady that question, but not at tomorrow's party though; otherwise you'd be committing what in my family is called lol a party foul.

Emily: well, in that case I will watch your father's behavior carefully throughout tomorrow's party, and later in the week ask your mom about it, and then decide for myself whether your father is a true Don Juan or not, but for now, lol, please stop hitting the sauce when it comes to talking about your dad. He is after all your dad.

Carl: to the victor go the spoils then.

Emily: Okay.

"Don Juan" is truly one of Bryon's greatest poetic achievements. Sadly, the rustics that I taught could not even pronounce the title correctly, let alone grasp its meaning.