Once upon a time there was a place called Greece. Maybe you've heard of it. One of the many kingdoms located in Greece was known as Argos, and it's King was a total dickcheese. He and his wife had a daughter, but everyone knows that back in ancient times if you were the King and you couldn't father any babies with penises, then you were a miserable failure and were not successful in the task of being a real man. Such was the case with King Acrisius of Argos. So he visited the esteemed Oracle of Delphi and asked her what the deal was. The Oracle was like, "listen up King Idiot, not only are you not going to have a son, but your daughter is going to have a kid and he's going to grow up and kill you. So choke on that, you bitch!" Then the Oracle headbutted the King until he was unconscious.
The King woke up a few hours later face-down in a ditch and was like, "oh snap I better make sure my slut daughter doesn't have any damn kids!", which is pretty much how most fathers are these days. However, the King took it to the Xtreme and had is daughter locked up in a tower Rapunzel-style. Well if you know anything about ancient myth or history, you know that the Oracle at Delphi is never wrong, and nothing you can do will override the prophecy. This was no exception.
Since Zeus was a Ron Jeremy-esque man-whore back in the day, he decided he was going to try and get "in there" with the King's daughter. He took the form of a shower of gold and impregnated the princess. Personally this sounds like bullshit to me because everyone knows you can't get pregnant from a golden shower, but whatever. However it happened, she popped out a boy and named him Perseus.
Since it's never a good idea to have the son of a God whacked, the jackass King decides it's far more humane to lock his daughter and infant grandson in a giant pine box and chuck it into the Aegean Sea. The box floats around for a while, until one day it's picked up by a fisherman who just so happens to be the brother of the King of the island of Seriphos. He takes the Princess and her son in and they all chill out at his pad and eat some sea bass or trout or mackerel or something.
Eventually King Polydectes of Seriphos meets the Princess and decides he's going to try to do her. However, Perseus is like, "Hey, King Poly-dick-cheese, lay off my mom your I'll bust you in the motherfucking mouth, OK?" Polydectes quickly decides he needs to get Perseus up off his bozack if he ever wants to score with the princess, so he gives Perseus a freaking ridiculous quest from which he will never return - he orders him to go get the head of the hideous Gorgon monster Medusa, a foul creature who's gaze turns any living creature to stone, and bring it back to Seriphos.
Perseus is like "whatever, chump" and heads out to get the head of the Medusa. Unfortunately, after a couple days wandering around in the wilderness like The Crocodile Hunter Steve Irwin he realizes that he has no fucking clue how to find the Medusa, let alone kill it. He gets super pissed and crushes a soda can on his forehead. Athena, the most badass of all the Greek gods, then decides to swoop in and help out Perseus because she's just good like that. She tells him that he needs to seek out the Gorgon's sisters - a group of three old hags with only one eye and one tooth between them, which they just pass around like those weird dancing muppets in Labyrinth. She also hooks him up with heir reflective mirrored shield, a pimp-ass adamantium sickle with a skull-and-crossbones embossed on it and a pair of "Air Hermes"-brand winged shoes.
Perseus meets up with the three one-eyed bitches and is like, "gimme some cool shit and how the fuck do I get to the Gorgon's Lair", but the hags of course just tell him to go hump a donkey. Perseus gets fed up with their crap, steals their eye, and threatens to eat it if they don't tell him where this Medusa chick is hiding. They agree, and before he leaves they give him a Helm of Invisibility +4 and two handfuls of homemade curly fries because he's so awesome.
Finally Perseus arrives at the Medusa's lair, which is completely surrounded by a forest of stone men and animals that have all been petrified by the Gorgon's gaze. He pushes on, using the mirror on his shield to avoid looking directly at anything that could make him hard, until he reaches the inner sanctum of the Gorgons. He finds Medusa and her two Gorgon sisters all asleep, and so he nobly sneaks in and kills the Medusa before she can wake up. When she dies, a fucking crazy-ass winged Pegasus horse flies out of her body cavity, which of course wakes up all of her friends. Perseus barely has time to yell "shiiiiiiiiit!" before popping on his helmet, becoming invisible Frodo-style, and running away like a little bitch. To his credit, the other two Gorgons are impervious to conventional weapons, so sometimes it's true what they say about cowardice being the better part of valor when you have absolutely no fucking chance of killing your enemies.
Perseus chucks the Medusa's head into his gym bag and starts flying home on his new Pegasus. He's not flying long though before he sees something that most commuters don't see on a day-to-day basis: a hot naked babe chained to a rock. Being the selfless hero that he is, Perseus decides to scope out the situation. He swoops down, exclaiming, "O virgin, undeserving of those chains, but rather of such as bind fond lovers together, tell me, I beseech you, your name, and the name of your country, and why you are thus bound.", which is essentially "hero talk" for "what the hell is going on here?"
"Help me Obi-Wan, you're my only hope."
Apparently the Greek Queen Cassiopeia pissed off Poseidon by talking about how much hotter she is than Poseidon's kids (and you know how parents can be). So in an effort of appease the mighty water god, they chained the Princess Andromeda to a rock so she could be eaten by a sea monster, because apparently that sort of thing really gets Poseidon off. Well Perseus wasn't going to have any of that. No true badass can sit around while a damsel is in distress, so Perseus flips out and attacks the sea monster by jumping on it's back and stabbing the shit out of it while it thrashes around in the water trying to knock him off. But Perseus is kick-ass, and eventually the repeated stab wounds are enough to fell the beast. Perseus frees Andromeda and since she thinks he has a totally sweet ride and some bitchin' shoes they decide to get married.
But shit is never that easy for a guy like Perseus. While he and his new wife are getting down with the phat beats at their wedding her ex-boyfriend Phineus shows up with some of his drunk asshole friends and try and start some shit. Andromeda tries to tell Phineus that it's over between them and that he needs to move on with his life but instead he decides to whip out his sword and start hacking up wedding guests. Before he gets the chance though, Perseus whips out the Medusa's head and turns Phineus and his crew to stone. A hush falls over the crowd when they see what Perseus has done. He looks around, breaks the tension with an insanely witty penis joke insinuating that Phineus no longer has to worry about erectile dysfunction and the party goes on until like 4 in the morning. Opa!
"Is that a severed head? What the hell are you doing with a... OH SNAP!!"
Eventually Perseus and Andromeda come back to Seriphos to show King Polydectes what's up. They arrive to find out that the King is still hitting on Perseus' mom all the time despite the fact that she's "just not that into him", so Perseus goes off to kick the King's ass. He walks into the throne room, pulls out the head of the Medusa, holds it up to the King and triumphantly says, "hey I found that thing you asked me to get for you." Polydectes turns to stone immediately, and then Perseus lets out a belch so powerful that it shatters the stone King into a million pieces.
Perseus and Andromeda would go on to rule the Kingdom of Mycenae for many years, and would be much loved by their people. No longer having any reason to carry a severed head around in his backpack, Perseus gave it to Athena, who bolted it to her Aegis.
Perseus is a badass because he didn't fuck around when it came to having a balls-out adventure. He slew monsters, saved damsels, beat up his wife's ex-boyfriend and fought the dude who was hitting on his mom. He outwitted the witches, he out-muscled the sea monster and he out-romanced his wife's prime suitor. He was the total package; and unstoppable warrior who got the girl and defended everyone's honor. Truly a badass.
Encyclopedia of Greek Myth
Mythography of Perseus and Andromeda
Perseus is so badass that chicks' clothes just fly right off when they see him.