A Russian fisherman posted last month a video on his Instagram showing a monster-looking creature sitting on the railing of his trawler.

Netizens reacted to the video clip, calling the animal resembling the character Megamind in the movie “Mars Attack” an alien. A commenter said it was a pet of underwater aliens.

Roman Fedortsov corrected them by identifying it as a smooth lumpsucker (Aptocyclus ventricosus), a North Pacific deep sea fish with a round and lumpy body, and adhesive pelvic fins that help them cling to surfaces.

Rapid pressurization during its ascent to the surface changed the physical appearance of the fish, according to the New York Post (NYP).

Meanwhile, the United States Fish and Wildlife Service (USFWS) revealed another monster fish in its Facebook post on 25 February.

Officers of the agency were surveying the waters of Presque Isle State Park in Lake Erie, Pennsylvania when they caught the invasive species.

They warned against dumping such fish in ponds and lakes because it steals the food of native fish and turns the waters murky.

“If you can’t keep your fish, rehome it,” USFWS said in a statement, according to NYP. “Just don’t let it loose.”

The agency was referring to a massive goldfish they called a “megalodon,” the term for a massive prehistoric shark.

USFWS officials believe the goldfish had been in the lake for two years.