Like most things, this all starts with a dream: specifically a dream wherein Ari and Walker were shrunk down to GI Joe-size and went on awesome adventures like sledding around in a hubcap and shit.
Then I woke up and was delighted, and realized that if Ari and Walker were somehow shrunk it would probably be Peter's fault in some way. And there might be even more Bros and others involved.
PONDER ON THIS AND ON TINY KINGDOM ADVENTURES.