Meme Hoarder lore:
This is the product of some of Redi and Knifeboi's experiments combined. They were working together on a project, Knifeboi had collected some memes, to try and make another amalgameme, Redi decided to help by putting it all together into one sentient being. But this experiment backfired. Nobody really knows what happened but there was a big explosion in the lab, and then the Meme Hoarder was there. Redi assumes that the explosion occured because the memes somehow joined together and made a black hole, this black hole is special though because it has sentience. It escaped the lab and began collecting more memes to make his arsenal bigger