Dean's Monster Mashups
It's like a Khan worm on steroids.
An intelligent parasite that can control its human host. Dean dubbed it the Khan Worm due to its resemblance to the Ceti eel from the Star Trek movie The Wrath of Khan. They were encountered by Bobby, Rufus, Samuel and the Winchesters  and later Cole Trenton is infected by a Khan Worm variant.
That's your excuse for leaving me with those gorilla-wolves?
Bobby: Well, congrats. You discovered it, you get to name it.
Dean: Jefferson Starships. Because they're horrible and hard to kill.
Octovamp and Vamptopus
So what are we looking for? Octovamp? Vamptopus?
Seriously. Dractopus. Seabiscuit the impaler. Land shark – what's next?
Dean has plenty of material to work with when the Winchesters investigate a series of murders based on childrens' drawings.
Dean: Vampire pirates. That's what you guys are. Vampirates!
Benny: You know all the years we ran together, I can't believe nobody ever thought of that.Benny: No, it isn't.
Dean: What do you mean? It's like the third thing you say!
Benny Lafitte was turned into a vampire by his maker, a centuries-old vampire known as "the Old Man." The nest of vampires he ruled over would find private yachts heading for far away destinations, feed on the owners, and then sink the boat to cover up their crimes. Dean brilliantly dubs them vampirates!
Were-pires and Ghoul-pires
Sam: So, what? We're looking at a-a werewolf/vampire hybrid?
Dean: Say it with me -- a were-pire. Huh?Sam: I'm not saying that.
Dean: Come on.
Castiel: It's a nachzehrer.
Sam: Come again?Dean: A Ghoul-pire! Right?
Castiel: A ghoul and vampire-like creature.
It turns out the monster the boys are hunting is neither a were-pire nor a ghoul-pire but the less sexily named nachzehrer.
Dean: So Sparkle is a unicorn and also a man?
Linda: Yeah.Dean: So, a manicorn.
Sparkle is actually a zanna but "manicorn" is a pretty inspired moniker!