From Team Fortress Wiki
Oops! Zat was not medicine!
— The Medic realizing what the suspicious green fluid is
The Emerald Jarate is a miscellaneous item for the Medic. It is an attachment for the Medic's Medi Gun and Quick-Fix backpack, that adds a pair of flasks full of glowing, neon green liquid and two crooked antennae jutting out from the coils on top. The Medic's emblem is replaced with four team-colored screws arranged in a cross.
This item can only be worn around Halloween or during a Full Moon; at other times of the year, it does not appear in gameplay, unless the server has Halloween mode enabled. However, it can be equipped at any time and can still be viewed on the loadout screen even when it is not visible during games.
October 27, 2011 Patch (Very Scary Halloween Special)
- The Emerald Jarate was added to the game.
- When equipped with the Quick-Fix, the whole loadout disappears on the class selection screen, while the Emerald Jarate is still visible.