Like its pre-evolution Solosis, its inner body is pale green in color with a darker green, jelly-like mass surrounding it. An unattached pale green segment floats above its head. It now has two, stubby arms and the red diamond shape in the middle of its head remains.
Duosion's name is a combination of "duo" and "fusion," mainly due to its differing change and genetic appearance from its pre-evolution, Solosis. Its title, the Mitosis Pokémon, is sourced from mitosis, which is the process in which two eukaryotic cells split and share genetic material.
Duosion is similar to Magneton and Klinklang in that more than one of its pre-evolved form forms together to make its evolution.