Does anyone have any theories on why this happened?

I actually thought this may have been an ok idea.

Nintendo's stock is down 20% since Super Mario Run came out

http://money.cnn.com/2016/12/19/technology/super-mario-run-nintendo-share-price/index.html

~update: Seems the stock has continued to drop...let me know if 20 is incorrect...

Well stocks are dependent based on investors "thoughts" and not exactly on how much a thing earns for them.......for example investors thought it would be downloaded 50 million times.....and earn SO MUCH more money off of it....but it's not even coming close. Analyst have sucked all year trying to figure things out....same happened with Pokémon Go. Anaylyst are why things are dropping

I heard Rol has the scoop on this.

So, despite winning a decent amount of change, getting all the brand advertisement the mobile market can get, and being one of the biggest paid apps right now (and still having to release on Android), the investers think this is somehow bad? What did they expect, Pokemon Go level of success? These two apps are very different. Investers sure are picky.

They probably expected more, there's already thousands of games like this on the app store.

This.

Analysts don't have a single clue how much anything is gonna be bought or downloaded they didn't even take in to account about the paywall.

Go was downloaded so much because it was free and it was pokemon that's it it was nothing new,if it was anything else called it wouldn't even reach a mil.

But with mario there is a paywall and it's 10$ anything above free or 0.99$ on phones it's gtfo.

Stock prices are a reflection of investors' expectations for the future.  So, the day before Run came out, the bid/ask prices of Nintendo stock factored in X number of downloads of run, resulting in Y dollars of revenue and profit.  Once the game launched, investors have real data to work with, rather than guesses and estimates.  So, the bid/ask prices are adjusted accordingly.  

In other words, its not about investors thinking its bad.  It is about the results falling short of expectations.  

I think many gamers who never invested before anticipated a surge after seeing Poke Go and thought it would be the same so they bought tons of Nintendo shares days before the release.

Now they must feel the burn. :/

I know. I'm just wondering what kind of expectations did they have, and what were they based on, because an 11% decrease of the stock's value is a pretty decent amount. Just how dettached from reality are they, or just how greedy can they get, if they consider a small app that is basically a runner game (with thousands of those free already) earning millions in a couple of days, when the cost is probably less than a million in total.

Investors. It's always those pesky investors.