Jack O' Melons are used as a decoration during Summerween. They're similar to a Jack O' Lantern, except they are made from watermelons instead of pumpkins. In the summer, the Gravity Falls residents light up Jack O' Melons for the holiday of Summerween.
Traditionally, Jack O' Lanterns are made out of pumpkins. Yet, for Summerween, Jack O' Melons are made with watermelons, hence their name. The first Jack O' Melon displayed in the episode Summerween was the one held up by the Summerween Trickster, which he used to threaten the gang. The remaining Jack O' Melons are seen throughout the town of Gravity Falls, where residential homes are decorated with them in spirit of the holiday. The last Jack O' Melon seen is at Old Man McGucket's house, in which Grenda steals it from him forcefully to prevent the last Jack O'Melon from being blown out (though this effort fails in the end).
Jack O' Melons resemble Jack O' Lanterns, except Jack O' Melons are made from watermelons instead of pumpkins. They both have faces carved into them and a lit candle inside them.
- 112. "Summerween"