Is our demogorgon Dart? (My Big dumb theory time)
[Spoiler alert, this involves alot to due with Stranger Things, and what I know currently of the show, stop reading here if you plan on watching Stranger Things]
If you don't remember Dart, its pretty much Dustin's pet Demodog
Dart, when he dies, is in the "DemoDog" state of the Demogorgon's evolution stage, which they are like a small tadpole at start, and slowly evolve like a pokemon up to the Demogorgon stage.
Here is where the theory starts according to Add-ons for "The Demogorgon" and the background for the entity
If I am correct, The Entity can take anything when it reaches near its death, and due to Dart dying in the show, the entity could have taken dart and helped raise it to the Demogorgon stage and made it into a killer. Demogorgon also has an Add-on called "Mew's guts", an uncommon add-on, but the only Demo that ate Mew the cat, not the pokemon Mew, is Dart, so why would some random Demogorgon have the guts of the cat they didn't eat?
This is currently all the evidence I have with proof of our Demogorgon actually being Dart