Gelatinous Cubes came into being when a 1-inch cube of Lime Jello fell on a dungeon map* during an early Gary Gygax rpg session. It totally enveloped the miniature for the mage Bigby. Rather than clear it up, Gygax told Bigby’s player he had been enveloped by a monster, and was dissolving.
This is why the Wizard Spell Compendium books mentioned the spell Bigby’s Transform Gelatinous Cube to Edible Gelatin***
*totally not a fact
**If it has been a wilderness map, Gelatinous Cubes would be 30-feet square. This is true, even though the actual story isn’t.
***Go ahead, go check for that. I the forward, they didn’t actually include the spell.