A cute, shiny Ditto with perfect IVs who was-- unsurpisingly-- used exclusively for breeding with other Pokemon.
However, the daycare handler accidentally left the doors wide open one day, and so the Ditto escaped.
Now they roam free, seeking out lots of new Pokemon (or, you know, whoever's cute~) to breed with and make lots of eggs.
Ditto is genderless but character and player prefer if Shiny is referred to as "he". Expect gooey trap Ditto dickings.