According to Where the Footprints End, by Cutchin and Renner, Bigfoot sightings and UFO sightings often occur together, or at least in proximity. The idea that Bigfoot is a big hairy ape is just one hypothesis, if the most popular and famous one. But there are a lot of sightings that bleed over into the paranormal.

(I'm not a believer, rather I just find the blurriness of the lines between folkloric 'things' to be interesting.)