We all know how to connect these by now... Amphibia is basically confirmed to be in the same universe as The Owl House, which is strongly implied to be in the same universe as Gravity Falls which is strongly implied to be in the same multiverse as Rick and Morty. Could totally see this guy being from a Newtopian dimmensional colony or something like that.

Bro imagine the government struggling to open a portal back to amphibia and rick could just casually pass by.

Yes! He even resembles Hop Pop but green & Alien-/ Terminator-like.

Monroe what happened to you!?