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.
A miniature of an Old Gateau and its packaging was included in the Sinnoh goods set from the Pokémon World Market merchandise line that was made by Re-Ment and exclusive to the Pokémon Center.
Edible Old Gateaux (Yōkan) have also been released in 2017 and 2021 and were exclusive to the Pokémon Center.
Pokémon World Market (Sinnoh goods set)
Delicious Adventure Munchlax
Delicious Adventure Munchlax (side view)
Edible Old Gateaux released in 2017
Edible Old Gateaux released in 2021
Trivia
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]
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."