I'm glad they didn't. I have no idea if it would sell more if they did, certainly it would sell more if they released it on other platforms, much more than any boost from slapping Mario/whatever milked out Nintendo characters they might include. Nintendo likes to say they are about "fun" (e.g. explaining why they haven't enabled Twitch streaming, although somehow PR presentations streamed on Twitch are "fun"), fixating on indefinitely milking a narrow range of pretty arbitrary characters is not "fun" it just unimaginative, FUN is "fun", and that's what this game seems about. I think the blooper/squid cross-over is interesting though, because it does have some cross over, but isn't necessarily "in your face", i.e. gratuitious IP placement. The interview with the designers seemed to indicate the squid concept was rather ad-hoc, not like an imposition of IP for it's own sake, but an organic development from the imagery/ideas of the game itself. What it does is allow some future game, possibly in some different genre, to explore some further blending of Splatoon and other Nintendo IP, which is plausible IMHO... But the point is not to over-do it... They should be appealing to new players have no attachment to the previous IPs.