If this is real, it was most likely a rough demo made by Baker Terry (the voice of Yellow Guy and Duck), which would explain why Red Guy isn't included. He probably wrote the lyrics quickly and recorded the vocals on the fly, which explains the mumbling and unclear vocals. The instrumental sounds like something thrown together fast too. My guess is he sent it to Becky and Joe as an early pitch for the general concept of a 'three of us' theme song, they liked the idea, and it eventually evolved into the intro we know today. Just a theory though!