Thanks very much!
The idea for how the "relay" is gonna work is that after you beat a level, you get given a "save code" which has all of the saved info encoded in it (all of the players' names, the rats everyone has chosen, which parts have been acquired, and how each part has been customized), that can then be passed on to one of the player's friends (via text, email, DM, etc.).
When that friend boots up the game, they'll be able to input the save code, and then they'll get to create their own rat and join that same relay (seeing the part their friend found and customized, before getting to find and customize a part themselves).
After that friend beats their level, they then get a new save code and can pass that code either onward to another friend or pass it back to the first person in the relay, and then the game gets passed around some more until all 4 parts have been found and the rats escape