Meeting your girlfriend's parents is never something you eagerly anticipate. But it could be worse. Take comfort in knowing that actually meeting your girlfriend's parents will not be as bad as these three examples.
Your girlfriend's mom might end up being the bane of your existence, but she probably won't exist only in your girlfriend's fractured psyche. You show up at your girlfriend's parents' house, and you see the silhouette of an old woman in a window. Your girlfriend tells you that's her mother, but unfortunately she's too sick to come to dinner tonight. Thinking you dodged a bullet by not having to eat dinner with a sick, old lady, you decide to celebrate with a shower. Suddenly your girlfriend ruins everything by stabbing you to death while wearing her mother's dress and a wig. She then puts your body in the trunk of a car and dumps you in a lake. A few days later, your sister and her boyfriend go to the house to look for you. They don't find you, but they do find the mummified remains of your girlfriend's mom in the basement.
This can only happen to you if you're dating a cougar. One night at a party a drunk guy hints that you're adopted. Naturally, you go to a psychic to find out if it's true. She tells you that you're destined to murder your dad and have sex with your mom. "Yikes," you think, "I better skip town before I kill my dad and bang my mom!" Now you're a ramblin' man on the open road. One day you and another car pull up to an intersection at the same time. You argue about who has the right of way, but eventually you get tired of arguing and kill the other driver. A few days later you enter a riddle solving contest and win! As your prize, you get to marry a queen whose first husband was murdered at an intersection. "What a crazy coincidence!" you think to yourself. The marriage starts off OK and you have some kids. But all relationships have issues. In your case it turns out that you are adopted and that you killed your real dad at that intersection and married your mom. Once you realize that the psychic and drunk guy were right, you shout, "Gross!" and gouge out your own eyes.
If you've only made out with a girl, don't meet her dad or he might cut your hand off. During an intergalactic war, you develop a crush on a princess. You doubt anything will happen because you're a farmer with low self-esteem, and there's a more attractive and confident space pirate who's also interested. But after a few years, you kiss a couple times! You're on cloud nine! One day you get in a sword fight with the leader of the evil empire. You think if you kill this guy you might get more than a kiss. Then he cuts off your hand, tells you he's your dad and asks if you want some help. You're really depressed now because your dad is an evil jerk and you still can't get laid. A few years later this ends up being a good thing when your friend's ghost tells you that the princess is actually your sister.