The Secret Of Growtopia is a consumable item. When used, it reveals a "mysterious secret" and writes it in your chat box. The secret is a random piece of information, and it can be about a certain item, the game, or an irrelevant topic.
The Secret Of Growtopia item is a part of the "Spoiler Alert!" Special Event. When it occurs, ten instances of the item appear in the world, and players are given thirty seconds to collect them before they disappear. When a player picks one up, it is announced to everybody in the world.