Ditto isn't the only Pokemon transforming in Pokemon Go.
Multiple players are reporting that Pokemon are mysteriously changing from one species to another in the middle of their 30 minute "spawn window." These transforming Pokemon are strange because, at least according to those using trackers, they retain their original set of IVs and still disappear when their original 30 minute window is up.
Originally it was believed that these transformations were "weather spawns" and that the Pokemon switched species due to a change in weather. However, now it seems that weather isn't causing the mid-spawn switch as players following the odd phenomenon aren't seeing any changes when the switches occur.
The changes are affecting both common and uncommon Pokemon. We've seen reports of Pokemon like Ralts, Unown, Slakoth, and Venonat suddenly transforming into another Pokemon without warning.
Some players believe this to be Niantic's way of fighting back against third-party trackers, but the changes seem to random and affect too many Pokemon to be an anti-cheat system. It would be one thing if only rare Pokemon were suddenly transforming, but the transformations are happening to mundane Pokemon too.
While it's easy to dismiss this bug as only affecting players who use trackers to keep an eye on the Pokemon that appear in their neighborhood, this bug can impact players who play without any help from third-party sources. After all, it would be frustrating to see an Unown nearby, only for it to transform into a Zigzagoon before you can catch it.
Niantic has yet to comment on these weird transformations - but it looks like this is the next big Pokemon Go bug. Let's just hope we get a fix before it affects more players.