Monsters from [[Undertale]].

[spoiler]Since they are found with the other amalgamates and also look like a collection of melted-together creatures, it is assumed that they are more of those accidents from the experiments with Determination.  However, they are the only amalgamates whose component parts do not resemble anything in the game, and there is no in-game explanation for this either.  This has led to several theories as to exactly what they are and where they came from.[/spoiler]
memoryhead