They only look that way thanks to explosive decompression. Most blobfish are pulled up too quickly and end up expanding like that. At their normal pressures they look like almost any other fish.

https://en.m.wikipedia.org/wiki/Psychrolutes_marcidus

If you have seen Adventure Time, I suspect the sea lards are probably based on blob fish. I don't have a source to back it up other than the sea lard's visual aesthetic and my recollection that Adventure Time and Blob Fish were both in the public consciousness as memes around the same time a decade ago.