I am known by many names

It's good that they remembered, because I sure didn't.

I actually got my players to remember the name of the evil dragon, and the name is by no means easy! “Ildrephu”

It helped that the dragon itself became VERY memorable, having developed a philosophy around how to best torture people based on Ben “Yahtzee” Crowshaw’s Chzo mythos. And then instead of fighting the party when they came to storm his lair, it invited them in, fed them, gave them nice accommodations, and made a binding magical contract with them for favorable terms… that tricked them into unleashing the Tarrasque back into the world from its divine prison. And then Ildrephu reneged on its half of the contract anyway, trusting he was strong enough to simply tank the magical backlash breaking the contract would do to him. Escaping the tarrasque and returning to Ildrephu to now be able to fight him at all due to being magically weakened was a highlight of the campaign.

They still talk about him, IRL years later. One of my finest quests I’ve given, and the fact that they remember his name when it’s such a non-English name really hammers in how much of an impression I left with him. It makes me so happy!

I made a villain probably more than 15 years ago at this point that, to this day, any player who was in that campaign will promptly tell me "fuck you" if I mention him or do a little flourish with my finger.

Philip the Brigand! He was born of several suggestions for memorability. A title, not just a name. Personality flair (such as, but not limited to, the flourish), and a knack for escape being the three I remember. Not plot armor, for sure. A great eye for knowing when the battle wasn't going his way though, which was usually shortly after ruining the party's day. Like when he loosed a rust monster that destroyed the fighter's treasured sword and also broke the monk's arm.

Mostly they pictured an incredibly annoying version of Autolycus from Xena/Hercules. Not unfair.

Mordecai

It is great.

Except they invariably latch onto the one character who is only covered in my GM notes as "try to remember to toss a generic cleric NPC into the tavern on the mountainside if the party needs healed mid-session".

"Oh, you mean that John McHealsAllott. Yes, he's still here. No, you're not able to get him to open up about his past."

Goblin’ Roblin the gay Hobgoblin.

Same but for when I remember the name of my own npcs.