Glitched Pokemon in pokemon yellow?

Several years ago when i was playing pokemon yellow i dropped my game by accident, then when I booted it up it was full of viruses and glitches to the point of it being entirely impossible impossible to play. Now the thing I was most interested in was all the glitched pokemon in the PC boxes, I found one in particular, it was a pokemon with a glitched name, and a sprite that looked like a shaded in square with a banana with legs and eyes, I thought it was just a coincidence until I took it into a battle only to notice it had a back sprite too, I thought it was odd, I want to know if this has been a confirmed glitch and if anyone else has had this glitch, also it wasn't metapod it, the front and backsprites were different to metapods. Tlso if you have a picture of it then link it as well please.