Given the subject matter that this song originally has, it's no wonder there's been no covers of it yet. It's difficult to make a good cover of a song that references child abuse without making it make sense. So that's why I think Red Guy and Yellow Guy would be pretty fitting for this. They've both been abused by the living nightmare they're trapped in, after all.
And as for Duck not being here... that's mainly because I didn't have his chromatic scale. But you could also see this as taking place in the "Death" episode of the TV show, where Duck is dead and it's mostly just the other two.
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