Okay, so I tried out random Gameshark codes on the emulator Pokemon Red.
It spawned a juggler- and his first Pokemon was a glitchy that had the sprite of Tentacruel.
I searched this one up- the first couple of digits were matching to the Tentacruel glitch Pokemon, but then the Pokemon had a picture digit that didn't match the one on Bulbapedia.
It was level 111.
This was Bulbapedia's glitch tentacruel:Attachment 90488
And this is mine:
Oh, and by the way, here is the GameShark code, for reference:
Notice that the little green square is missing from my Tentacruel glitch.