Eggs have long track record of doing weird things in Pokémon, and it seems the eggs of Pokémon Go are no exception. Players have somehow managed to place eggs inside of Gyms instead of regular Pokémon, and worse still the eggs have proven to invulnerable making the Gym impossible to take over.
At least four Gyms around New York City have been taken over with an egg by a level 5 trainer by the name of kikNetopsG. Players have also reported on Reddit that merely checking in on an egg-infested Gym causes the game to glitch and lock up, forcing players to quit and restart the game.
Kotaku speculated in their report that placing eggs in gyms may constitute cheating, and with the recent wave of players being banned from Pokémon Go this may be one glitch you don’t want to be a part of.