Squash Serum

Squash Serum is an item included in the Halloween update. It is traded by the Necrid Horsemen collectors in each of the major cities (except The Amnoon Oasis): It causes a translucent Jack-o'-lantern with a sparkling stem to appear around your character's head for a brief time. Squash Serum has no other effects.
 * Horseman Nurmangor in Ascalon City for 3 Charr Carvings
 * Horseman Irumund in Ascalon City for 2 Ornate Grawl Necklaces
 * Horseman Vulgamor in Lion's Arch for 3 Decayed Orr Emblems
 * Horseman Saralim in the Henge of Denravi for 2 Maguuma Manes
 * Horseman Calstein in Droknar's Forge for 2 Stone Summit Badges
 * Horseman Vilneous in Droknar's Forge for 1 Feathered Avicara Scalps

It is unknown how long this will be included in the game. Most likely it will be removed after Halloween. This may make hoarding it now and selling it later quite profitable.