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It first appeared in "7 Continents for 7 Koopas". Having ordered each of his kids to take over one of the Real World's seven continents, Bowser ordered Kootie Pie Koopa to wreck havoc in Europe. Kootie Pie complied by heading to the Louvre, where she transformed all of the artwork into portraits of herself. Those that were shown were:
Later on, Mario came by to steal Kootie Pie's magic wand, and used it to restore all of the original artwork. He also created a wave of water from the Birth of Kootie, which washed Kootie Pie out of the Louvre.
The Louvre also briefly appeared in the episode "Super Koopa". Bowser had invited his kids to run ammuck in Paris, so Hip and Hop traveled to the Louvre, where they employed Paragoombas to remove many of the original paintings. Hop was seen putting up some of his own so-called "masterpieces", while Hip was seen vandalizing the Mona Lisa.
Although Hip and Hop eventually left the Louvre, it was never shown as to how the original artwork was restored to the museum.