This happens when the hexadecimal value of Unown is D0. The Trainer in Trainer House hasn't a valid name, and has a glitch party. When I used "Recover" even if it was pointless, Meowth used a glitch move that reset the game in a glitch dimension. The colour of this glitch dimension is the same colour of Meowth's sprite. Anyway, this Trainer can be defeated with a strong and quick Pokémon.