Now this might not be creative, or anything remotely original, but why not just use Super Smash Brother characters in a chat group (if it exists and you know it please send me a link, I'll read it)
You can start with the original cast, then add more and more to the group. You can even use them at the start of their journey so that they have a helping hand during it. (Like mario needing help with a level or something.)
Well to be fair, most of these games don't mix. Someone like game & watch probably wouldn't need help in his game, and I won't even mention R.O.B.
If you want to be more interesting, you can just make the person who asked for help actually pay with the rewards from his world (like a fire flower or something), if you are a good writer who can balance things out then go for the multiverse rewards like almost every multiverse group chat does.
I am kinda out of ideas for the moment if anyone is even reading this. I'll release whenever i want.
Also not having drinkable tapwater sucks if you drink a lot of water. Most cheap bottled water taste really bad and you have to pay more for mineral water which taste better. This isn't an idea this is just a rant.