• English / United States: Jessie's Gourgeist
• Japanese / Japan: ムサシのパンプジン
• Japanese (Romanized) / Japan: Musashi no Pumpjin
• Japanese (TL) / Japan: Musashi's Pumpjin

Jessie's Gourgeist was first revealed in the Movie 18 short poster and then later appeared in the third XY ending. Jessie's Gourgeist is the evolved form of Jessie's Pumpkaboo.

Count Pumpka, the master of a castle in the Kalos region had been searching for a mate for his prince. The prince had fallen in love at first sight with Jessie's Pumpkaboo and Pumpka, ordered his butler to invite them to the castle to be introduced and to have a meal. Upon meeting them, Pumpka noticed that Jessie's Pumpkaboo was a truly excellent Bakeccha and that he'd never seen such a big one before.

He then asked Jessie to trade her Bakeccha so that the prince could wed her. Despite initial hesitation, Jessie agreed and traded her Bakeccha for his Kucheat because he told her that it is a Pokémon reported to mega evolve. During the trade process, Jessie's Pumpkaboo evolved into Jessie's Gourgeist. Pumpka then realized that Pumpjin is a trade evolution and the prince liked the way Bakeccha looked better. Jessie then realized that the bond between Pokémon and Trainer was strong between those two as she remember that it nursed her the whole night when she had a fever, fed her with ground fruit and was the only one to congratulate her on her birthday when everyone else forgot.