The Sykesville, Maryland monster flap began in the early summer of 1973. Tony Dorsey was the first witness to the monster on the evening of May 29 at his home on Norris Avenue. According to The Bigfoot Casebook by Janet and Colin Bord, Dorsey's sighting came after he witnessed a UFO dropping an object of some type into a reservoir. Mark Opsasnick notes that Dorsey saw two luminous red eyes about the size of half-dollars, but did not see any sort of body ("Monsters of Maryland: Bigfoot", Strange Magazine 3).
The Chestnut Ridge area, which is Pennsylvania's Bigfoot hotspot, has seen the bulk of the UFO-related sightings. One of these was in 1975 in Jeanette. On May 19, a motorist saw a Bigfoot running quadrupedally, later rising onto two legs and running off into the forest. A UFO had been sighted in Jeanette on May 18. Other reports of synchronous Bigfoot and UFO sightings were reported from Midland and Uniontown. In the 1974 Uniontown sighting, several individual Bigfoot creatures were seen, as was a UFO. When one Bigfoot was shot at, it disappeared into thin air. In 1975, a report from Jumonville surfaced of a Bigfoot creature which, oddly, floated rather than walked and was later enveloped by a mist. When the mist receded, the Bigfoot was gone. Could the mist have been a sort of UFO? Many of these sightings were collected and investigated by Stan Gordon.
The most famous and bizarre humanoid report in Gordon's files, though, took place on October 25, 1973 in the small town of Liesenring near Connelsville. I'll post the Pennsylvania Bigfoot Society's description of the incident:
A man and two boys saw a UFO land in a field. Upon investigating, they observed 2 tall, hairy bipedal creatures walking along a fence line. The creatures had matted, dirty brown hair, glowing green eyes, broad shoulders, and small necks. They walked stiff-legged giving them an overall robot-like appearance. The man shot at the creatures, which caused the spherical UFO that had landed in the field, to leave the area immediately. Although the witness felt he didn't miss, the shots had little effect on the strange creatures. They simply turned around and traversed their way back along the fence line. A luminescent ring on the ground remained where the UFO had once been. The witness left the area and returned later with a Pennsylvania State Trooper. Although the glowing ring near the ground was still visible, its intensity had diminished. Several hours later the luminescent ring completely dissipated.