I was catching a spinarak at the time and I was hoping it was a Ditto, even though I've never heard of someone catching one that was a Ditto, it wasn't but then I was hoping that the other known Ditto disguises were nearby and they weren't.
One time I was catching a Ratata and I swore I saw Ditto jiggling in the background and thought maybe that rat was a ditto but it fled so I never found out.
Another mystery, what's the deal with that other catch, the one where the ball rocks only once and the start come out in a streak? First I thought it was a glitch but it's been a few months now and I can't figure out why it happens