Well,I have made such a thing.Read below.
Lunatonamus created himself and, unconsciously, created all other dimensions. He then made his home. He got lonely, and
switched genders to lay 2 eggs.They hatched into Arceus and
Mew. They set aside each other to make their worlds. Arceus
and Mew got into a fight and Mew lost. He crashed into Tora,
his favorite region. He made a deep cavern.
Thousands of years later, Professor Oak's crazy uncle Professor Balsam Fir creates mutated pokemon on this region
then mysteriously disappears...