Most people who breed pokemon have used dittos, and since they are so frequently used people often leave them there. So I'm wondering if your ditto has been able to gain a ton of levels due to just being left in the daycare, particularly if you are hatching different eggs and thus doing a LOT of bike riding with them in the daycare the whole time. For me, I once got a ditto in B2 up to level 86 before I took it out, and it started at level 63- not the most levels, but at such HIGH levels like that it still is a ton of walking! How about you all?