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. Benny is impressed and surprised that none of the other vampires ever thought of calling themselves that before.
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.
Uh so Dean, I don't... I don't believe what you're hunting is a Whisper. Must be another creature of some kind. Okay. Fine, I'll say it. Maybe it is your so called were-pire but to be honest I have never heard of a creature of that name.
Castiel: It's a nachzehrer.
Sam: Come again?Dean: A Ghoul-pire! Right?
Castiel: A ghoul and vampire-like creature.
After discovering that they are dealing with a victim that is missing its heart and is drained of blood, Dean suggests, to Sam's annoyance, that they are dealing with a were-pire. Castiel eventually identifies the monster as a Whisper, causing Dean to try to get Castiel to call it a were-pire as well, to no avail. When Castiel reveals the actual name, Dean feels that it's lame compared to his were-pire. After realizing that he's wrong about it being a Whisper, Castiel suggests that maybe they really are dealing with Dean's were-pire.
It turns out the monster the boys are hunting is not a were-pire but the less sexily named nachzehrer, which Dean immediately dubs a ghoul-pire based off of Castiel's description. Dean later tells Lily Markham that the deputy was a ghoul-pire and he doesn't think the man's severed head can hurt her anymore.
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!
Eliot: So, if a werewolf bit a vampire who was also a shapeshifter?
Dean: Easy. Were-pire-shifter.Eliot: Of course.
Dean: You know what this is? Mimes. Evil mimes.
Sam: Or Vampires.Dean: Vamp-mimes! Son of a bitch!