In Pokémon: Magikarp Jump, Old Gateaux can appear as food that can be consumed by Magikarp. They are unlocked at Trainer Rank 73 and cost 429,910 to unlock.
Old Gateau's name in both English and Japanese is a pun based on the location it is found. In English, the French word gâteau ("cake") plays on Chateau. In Japanese, the Chateau's name is "Forest Manor" (Japanese: もりのようかん) while the Gateau's name is "Forest Yōkan" (Japanese: もりのヨウカン); the two terms are homophones and are pronounced as mori no yōkan.
Its French and Italian names also incorporates a pun between gateau and Chateau.
The English names of the Old Chateau and Old Gateau were coined by translator Nob Ogasawara, intending to preserve the pun in the original Japanese text.[1][2] According to Nob, he was able to keep the Old Chateau/Old Gateau pun in part due to him being able to give more input in the localization process from Generation III onward.[3]
According to the anime, the Old Gateau is also known as the "Mirage Gateau".
In the games, "Old Gateau" is usually pluralized as "Old Gateaux". However, the description of the Souvenir Set in Join Avenue says "A set of two Old Gateaus. The cake heals all the status problems of one Pokémon."