This video is by far the most convincing video I have ever seen. It was originally posted 12 years ago but has still managed to fetch a lot of views because it is scary as hell.
The video goes back to the 90's when a man was walking in the woods with his dog and he caught a swollen being, lying on the ground, bleeding. He was horrified to see that it was an alien. You never want these alien species to rule our planet, right?
He even heard a little yelp!
Watch the video in the end.