In an interview with Famitsu, Yuji Naka reminisced on when he pitched to Miyamoto a Mario and Sonic crossover before Mario and Sonic at the Olympics. They eventually got their wish with a couple of titles where they can be found together, but he still wants to see an platformer starring both. Interestingly enough, back when it was first pitched they had decided that: “clearly it isn’t necessary for Mario and Sonic to co-star in an action [game]”.
“Actually, I wanted Mario [and Sonic] to appear together, so one time I went to give Miyamoto-san a presentation on how I want to create an action game which is co-starred by Mario and Sonic. It was in the GameCube days, and I took around four planners with me. It is a pity that the discussion was ‘clearly it isn’t necessary for Mario and Sonic to co-star in an action [game]’ and it didn’t become a reality, but SEGA was able to get the license for the Olympics just at that time, so in order to make the best use of the license, companion characters appeared together. A little later Sonic appeared in Super Smash Bros. Brawl. However, this too came into reality because I requested from Sakurai-san, ‘I want Sonic to appear [in Smash Bros.]’. The Olympics is a bit different from my wish, but I think it’s a good thing that children around the world are happy about them co-starring. But someday I want to realize an action [game] together with Mario. I think I’m going to give another presentation so that Takashi [Iizuka] finds the necessity [of a Mario & Sonic action game] (laughs).”