Vaseline

David takes his motorbike to the bike shop and the clerk tells him that the gas tank lid is broken.

The clerk instructs David to seal the break with some vaseline whenever it starts to rain to prevent water from getting into the tank.

That night, David takes his motorbike to his girlfriend, Melissa's, house to meet her parents. As he pulls up, she comes to out to greet him and says "No matter what happens, don't say a word. Mom and Dad had a huge fight about the dishes twenty years ago and they both refuse to do them. The first person who speaks at the dinner table has to do the dishes. So no matter what, just keep your mouth shut!"

With that, David is taken inside where he is introduced to Melissa's father and mother. After a few minutes, dinner is served at they all sit down at the table, where there is complete silence.

David can't resist but have some fun, so about halfway through the meal, he sticks his hand down Melissa's shirt and fondles her for a moment. Although both parents are infuriated, neither of them say a word.

After a few more minutes, David decides to have some more fun. He reaches over and gives Melissa's mother the biggest Frenchie he possibly can. Both Melissa and her father and outraged, but remain quiet.

Moments pass and everyone is silent. David is smiling, when outside it begins to rain. Remembering his broken gas tank seal, he takes his container of vaseline and stands up.

Looking scared to death, Melissa's father jumps up and screams "ALL RIGHT, I'LL DO THE FUCKING DISHES!!!"