He's Godzilla, but a Skeleton. Simple.
Skeleton Godzilla was the original Godzilla, then he got killed by the Oxygen Destroyer.
Becoming a Cyborg
Go watch Godzilla Against Mechagodzilla and Tokyo SOS.
Being recruited by Death T-Rex
Death T-Rex sensed a being in Universe 986 that was both living and dead. That being was Kiryu. since he was in the market for minions, Death T-Rex ripped the Skeleton out of Kiryu and reaniated it as Skeleton Godzilla.
A T-Rex Halloween
Skeleton Godzilla, as well as Death T-Rex's other minions, were teleported to the spooky graveyard to fight T-Rex and his friends. Skeleton Godzilla tagged team with SkeleT-Rex for a little bit before Godzilla showed up. After defeating Shin Ghost Godzilla, Godzilla transformed into Super Super Godzilla and defeated Skeleton Godzilla with a single falcon punch. After the battle, the GDF took back the skeleton and rebuilt Kiryu.
- Ghostly Atomic Breath. This beam is white, like the original Godzilla's.
- Skeleton Godzilla is my second Skeletal Kaiju, after SkeleT-Rex.
- Skeleton Godzilla parodies an old fandom misconception that Godzilla's skeleton was an accurate depiction of Ghost Godzilla
- No spook scary skeleton jokes, I already beat everyone to it.