He is based on the Gloom-shroom, but like how Goop-shroom is different from Fume-shroom, Toxic Gloom-shroom is green instead of purple. He also has tiny yellow spots.
A beta icon in the game proves that Toxic Gloom-shroom was originally intended to be Gloom-shroom. It is unknown why the change was made.
His topmost, bottom, leftmost, and rightmost appendages are noticeably larger than the rest in his sticker pack image.
His figure variant (which was officially confirmed to be Toxic Gloom-shroom) looks more like the regular Gloom-shroom, as he is a purple color instead of the normal green color.