Comparison of the 2016 “Mario Pikachu” promotional art by the Pokémon Company (top) and the 1985 Super Mario Bros. Japanese box art, drawn by Shigeru Miyamoto (bottom), on which it is based.

In addition to replacing all characters from the original artwork with Pokémon that resemble them, there are subtler changes around the environment. The cliff on the left was replaced with the Cerulean Cave from Pokémon Red and Blue, the pipe below Mario was replaced with the Slowpoke Well from Pokémon Gold and Silver, and the castle behind Bowser was replaced with the Tin Tower/Bell Tower, also from Pokémon Gold and Silver. Main Blog | Twitter | Patreon | Store | Small Findings | Source: 1, 2