The Rat Pits Massacre, also known as the World 97 Massacre, was a glitch that occurred shortly after the release of Summoning. The glitch was activated by going to the Rat Pits in either Varrock or Port Sarim and having a player challenge another player, then disconnecting or logging out when their cat attacked the other player's cat or a rat. Upon logging back in, they would spawn outside the Rat Pits but their cat would retain the ability to attack other cats and Summoning familiars in the vicinity. If the familiar was carrying any items when it was killed, the player could pick the items up.
The massacre moved from Port Sarim, then Falador, then Taverley, then Varrock, and finally ended in Canifis when a Jagex Moderator disconnected the players and a system update followed. The players were not banned for this but received rollbacks on their accounts.