There was veey little that Vernon Dursley did not despise in his life. The aggressive, expensive-trousers-ruining chihuahua next door, the new employee at his company who alwas messed the coffee up, and the television whenever the thing needed to be repaired. Most of all, however, he disliked his wife's family, the Potters. A bunch of lunatic deviants who used "magic" and apparently had a whole underground society of which most normal people weren't aware. It should come as no surprise then, that Vernon absolutely did not want to go repair his sister-in-law's garden fence. After all, couldn't they just use magic or whatever it was to do that? Besides, he wouldn't help them even if they begged him to. But when James Potter had called Vernon thrice every hour for a week, he finally gave in. "But that will cost you a thousand bucks, mate!" he added angrily. A shoft chuckle from the other side of the telephone. Damn fool, Vernon thought to himself. The Potters are filthy rich, should've remembered. Should have asked a million.
So when Vernon arrived at Godric's Hollow, he was surprised to see the given adress was nowhere to be found. Damn wizards. Had he taken all of his fence-repairing stuff for this? He wanted to turn back and leave, when suddenly James Potter appeared out of thin air. 'There you are!' the young men greeted him jovially. 'Just in time to help with the fence!' Vernon mumbled something nasty before asking why they just didn't use magic. 'Oh, there's a serial killer who wants to murder my whole family, so that's why we only use magic when there is no other alternative. But don't be afraid, everything is alright.'
Vernon frowned at this utter nonsensical logics, but let it be. 'So, where is the house?' he demanded.
'Oh, yeah', James said. He said some kind of spell and then suddenly, a house appeared right in front of Vernon's nose. 'Argh!' he said, and the fell to the ground.
'Oh no', James said, horrified. 'Who will repair the fence now? Perhaps I should get the wheelbarrow from the shed and put him in bed for a few minutes.' It would prove to be a real nightmare for both him and Lily to toss Vernon in the wheelbarrow, drive it inside the house, and carry Vernon up the stairs. 'Why don't we just use magic?' Lily asked.
'Too dangerous, sweetheart', James replied. 'There's a serial killer after us.'
What they didn't know, however, was that Vernon was not actually unconscious. After all those days having been called thrice per hour, he was not only moody, but tired too. So what better time to get some sleep, and unknowingly tease his family-in-law, at once? Once he finally lay in the guest room's bed, Vernon could hardly surpress a chuckle. Man, I am so clever. It wouldn't be long before he dozed off.
A few hours later...
Two shady figures approached the still visible house in Godric's Hollow. One was tall and skinny and had a white face, the other was constantly making squaking noises. 'See?' the latter asked. 'That is where the Potters live. Do i now get my reward, Lord Voldemort?'
Voldemort sighed. 'Fine, Pettigrew. Go back home now. Fifty pounds of cheese will wait there for you.' Pettigrew made a noise of excitement and sprinted away. The dark Lord straightened up, walked towards the front door and blasted it away with a blasting spell.
Inside, Lily and James Potter, who were just playing with their little son, Harry, looked up in terror. 'Oh no!' James exclaimed. 'He has found us!'
'Quick!' Lily screamed. 'We must get out of here to a safe place!'
They quickly scrambled out of the living room, and took a different route to the hallway. 'Why didn't we just go outside through the kitchen?' Lily asked.
'Too late!' James replied. 'Maybe we can fly out of the window using our brooms or something.'
But that was not to be. Before they could go upstairs, Voldemort appeared right in front of him, red eyes and a sinister smile. 'Aha, my mortal enemy Harry Potter! Now we finally meet!'
'Please do not hurt him!' Lily cried, holding the infant boy close to her. 'He's just a child!'
Upstairs, in the guest room, a sleepy Vernon Dursley opened his eyes. He heard all of the screaming downstairs and he was furious. 'Can't these lunatics never be quiet for once!' But then he heard the unfamiliar voice, and remembered what James told him about the serial killer. 'Damn friggin' idiots!' As fast as he can, Vernon rummaged through his belongings (which Lily and James had also placed in the guest room). There, Vernon found his gun and sprinted out of the room, into the hallway. 'Hands up in the air!'
Voldemort, who was just about to use the Avada Kedavra curse, looked up in surprise, then amusement. 'And what do you think a fat Muggle like you can do to defeat the greastest wizard of all time?'
Vernon was so furious his entire face turned purple. 'I. AM. NOT. FAT!!!' He aimed and shot Voldemort in the head three times. The Dark Lord stumbled, fell backwards, and hit the ground, dead as a stone (apparently, the Horcruxes only work if the death is caused by magic). Lily, James and Harry sprinted towards Vernon to embrace him and thank him and kiss him. 'No!' he cried. 'Stop! I didn't do it for you! Stop!'
From that day on, Vernon Dursley would be known throughout the entire Wizarding World as "The Muggle who Defeated You-Know-Who." He appeared in all kinds of books, not one wizarding child would grow up without knowing his name, and once Harry was old enough, he was all too proud of his heroic uncle.
And as for Vernon Dursley himself...
... he solemny swore to never go repair someone's garden fence ever again.