Is one of three things.
Zilla, I don't recommend using this name, honestly. However, the implication is large and/or lizard hybrid.
Kong: The giant ape. The public domain GIANT APE (see Universal City Studios Inc. v. Nintendo). You really shouldn't have an issue.
As for origin stories. Mutated supervirus, growth hormone experiment gone out of control, human being regressed in experiment to recreate dinosaurs gone awry, radioactive contamination, really old, ancient lost God/Indian animal spirit, enlarging ray accident, teleportation gone awry, [getting into the weirder stuff now] man attempts to print a monkey with a 'matter deposition printer' and sets the scale wrong, teleportation and sets the scale wrong, teleports being from another dimension and (again) scale is wrong, test subect for nephlym (giant) dna reconstructed from bones, dinosaur.. hmm... unfrozen from a glacier, awakened as protector of an ancient temple, summoned by an evil wizard, alien that fell from space on a meteorite, alien that fell from space in a meteorite, alien caused by a magic or radioactive metorite, etc...
Dinosaur monkey hibrid?
"As you know, birds are some of the smartest creatures on earth. They can speak. It is our hope that by adding DNA from the south african macaw we will create a talking ape. We've found that there are incompatibilities initially, in an effort to achieve maximum compatibility we've added some genes from the closest relative of both monkeys and birds alive today."
And a new bridge for passing viruses from animals to humans is invented, everyone dies.
But seriously, if you can't take it from there you aren't fit to write sci-fi.
So, it can't be a giant monkey... as that would be silly, you can just call him 'Kong' and be done with it.
I suggest using a giant Gila monster. Though, I would be tempted to use my favorite, a Komodo Dragon.
Ooh, cool, the Komodo Dragon links to the whiptail which describes parthenogenesis, fascinating. Also, sharks have been known to reproduce by parthenogenesis.
Hmm, Fetiform Teratoma... I had a character who self-replicated by mitosis, but this seems more practical (and amusing), he creates a small version of himself, infant like, which then grows rapidly to full size.
Kong(a giant ape, my version, including all origin variations presented here), A slightly more anthropomorphized Gila Monster derived from the form of Kong and the general reptilian features of the giant Gila monster (Henceforth known as Kong-Gila!), and anything in this post are released into the public domain under the CC0 license.
If, however, kong-zilla is none of these... I can do naught! Also, if he has any unique depictions they would be copyrighted, but at the same time I will describe a few forms.
First is a clawed green monkey which sheds it's skin (possibly growing in size as it does). [Drawing from snakes here, don't know enough about lizards, mostly what I read on wikipedia]
Second is a giant ape/monkey of any species or variety, most likely gorilla or other heavy set ape.
Third is an anthropomorphization of a T-rex using simian features, most likely larger arms, humanoid, reptilian, or dinosaur? eyes, thermal vision (thrown in for fun), gripping claws (possibly, would be amusing, especially the feet), a more humanoid torso, a more humanoid pelvis (especially),
Finally, a draconic version of any of the above... with wings. Draco-kong. Bonus points if the wings are tiny and you use pseudo-science and bee's to explain why it can fly. That would be HILARIOUS (scientifically wrong, but hilarious. Bee's use vortices that only function on a small scale).
Copyright infringement is a two pronged test, typically availability plus similarity. Note: who defines similarity can be troublesome as enough random people saying it's similar can be a problem. The best thing to do is to simply make it unavailable to yourself. You can't always just 'change the background' and fix it. The character is still the character with or without a background. That's why you should always try to put as many insane ideas into your head as possible. One of my best characters honestly scares me.