Those people are being silly. A quick Google search will reveal that fans had already been making art featuring Bowser and elephant Peach getting it on months before this ad was released.

According to a translation shared by Twitter user @Gosokkyu, Miyao was provided just two images as reference materials: one was Peach’s 8-bit sprite from Super Mario Bros., while the other was ...

The art has been completely redone, from the core sprites of Mario and Luigi to the tiniest of background details, and the result is some of the most beautiful and vibrant 2D art around.

Bowser Jr. wasn’t introduced to the franchise until 2002’s Super Mario Sunshine, but the character fits really well with the Yoshi’s Island aesthetic, as @GBrothersStudio clearly demonstrates.