"Originally, I would look for paintings that were being discarded and use them as a cheap source of canvas, simply painting over them," the artist told Bored Panda. "Eventually, I came across a landscape painting that featured an open body of water in front of a few mountains and, feeling it was pretty decent but sort of empty, painted a sea serpent into it. After repeating the process a couple of times, I posted a set of three to Reddit, and wound up getting some attention for them. After that, I just stuck with the concept."

One of those first three, called Mountain Monster, really impressed Weezer, an American rock band from Los Angeles. In fact, the musicians loved it so much, they made it the cover of their 2014 album Everything Will Be Alright in the End.

"What I look for are actual acrylic or oil landscape paintings (no prints or reproductions - they tend to be more difficult to work with) that are 'complete', but have open areas in which to integrate some sort of giant beastie," McMahon said. "I like paintings that look like they were made by people watching Bob Ross videos."

"Generally speaking, I start by loosely sketching the original landscape on paper and then drawing a monster where I feel it should live in the painting," Mcmahon explained. "I try to set it up so the monster is interacting with the landscape in some way. I then draw the monster in charcoal onto the landscape painting and use sandpaper to smooth out any textures which the monster is in front of."

"I'll get a color palette ready, paint the monster, then do my best to repaint any elements of the landscape that should be in front of the monster for whatever reason (tree branches, foliage, water, etc.) or alter the landscape to make it appear 'lived in' (ripples in water, shadows, footprints)." If there's an existing signature, McMahon doesn't just hide it. He acknowledges the original artist by adding his own next to theirs.

He'll go and search for them in local thrift stores, auctions, rummage sales, etc. but never any actual art sales. "I avoid any art being sold by the original artists, looking more for art that's being thrown away or discarded. If I purchase a landscape painting to alter, I rarely pay more than $10."