The other dimension was the Doom universe. Doom Guy drags me along with him to Hell and shoots Cerberus. He then proceeds to blow up every other demon, hell-bent on killing Satan but I don't really care about that. I got the banana back. So I use my portal gun to take the banana to a black hole and throw it in.
I went back to my home dimension, an alternate universe where Earth never blew up, and hell still exists. With the help of my dad, Lucifer, I am transported to wherever that black hole leads to, which happens to be a quintessence field from Voltron. I grab the banana and give it to my favorite paladin, Pidge, to protect. She drops it into the Galra base right before it blows up. The banana is nowhere to be seen, but we know it was not destroyed. (We're getting a little fandom-y up in here, hope you don't mind)