In case you haven’t heard of it yet, the story behind it is this: a father and a son went to a park to film some red deer. The deer were not tame, but were used enough to humans in the park they wouldn’t automatically run away either. Well, they wouldn’t run away from humans, as you can see in the first few seconds of the video below — but they would run away, and in a stampede, if there was a dog chasing them. The dog’s name is Fenton, and the unfortunate fellow running after him and yelling is the proud owner. The father and son from the beginning of the story put the video they were making on YouTube, and the proud owner instantly became the “Fenton Jesus Christ Guy”. And immediately after that, plenty of stuff got “Fentoned” — if there’s a stampede or a fuss, you can be certain Fenton is behind it, while the unfortunate owner yells after him.
The best two “Fentoned” videos I found were Jurassic Park and the subtitled Hitler scene (though only about the first half of the latter is really fun, after that they start overdoing it).