We're not sure whether it's a glitch or whether Niantic's adding a bit of more character to Ditto, but the cute gelatinous, shape-shifting Pokemon seems to be a bit afraid of Pokemon Go's new Legendary Pokemon.
According to a thread on Reddit, gamers have been reporting strange Ditto transformations when the normal Pokemon is being used in Legendary Raids. Though most users say that Ditto generally transforms into a Legendary Pokemon in the game, the shape-shifter sometimes malfunctions and turns into weaker Pokemon like Pidgey, Magikarp and Hoothoot while fighting Legendary Birds like Lugia and Moltres.
While it's pretty questionable why some players would be using Ditto in Pokemon Go's Legendary Raids, it's uncertain why Ditto fails to transform on occasion. There isn't any good explanation why Ditto fails to transform properly on occasion – some say that Ditto can only transform into a Legendary Pokemon once per battle, while others say that the shape-shifter can only transform properly once a gamer catches a particular species of Legendary Pokemon in the gaming app.
Maybe the best thing Pokemon Go gamers can do for now is avoid joining Legendary Raids with Ditto in their team.