So I was testing a very lol Fossil deck, and got the following error-
The cards which were supposed to be banished (Neo-Spacian Grand Mole and Elemental Hero Absolute Zero) were not banished, and remained in the graveyard, while Skullgios was summoned. I was later able to use another Fossil Fusion and summon another Skullgios, this time targeting Masked Hero Acid and Neo-Spacian Grand Mole. I got the error again, and the Skullgios' summon went through.
Though this glitch did allow me to pull off an OTK, though...(http://i.imgur.com/hrWwJmA.jpg)