Reputation system

You could have an si controlling the system or just make in similar to the gold list systems.

Basically the reputation system appears in different worlds and show everyone the thoughts of 'higher dimensional beings'(people from the real world lol) whom have watched their past, present and future.

The characters can gain reward for good reputation etc you decide. Example in the Naruto world orochimaru's name comes up and the entire elemental nations see

Top 3 opinions

1. Pedophile and lover of young boys

2. Hard to kill like a cockroach

3. A good but crazy scientist

For Harry Potter Headmaster Albus Percival Wolfric Brian Dumbledore's name appears

Top 3 opinions

1. Secret dark lord

2. Pedophile and lover of young Hogwarts boys

3. Old man doing his best

It's a very open idea, you could use many worlds like Star Wars, fairy tail, one piece etc have fun with it.