From out of nowhere, Charles Schmidt, otherwise known as the guy who created Keyboard Cat, and Christopher Orlando Torres, known primarily as the guy who created Nyan Cat, are teaming up to the sue 5th Cell and Warner Bros, the developer and publisher of Scribblenauts respectively.
The following is bulk of the complaint, which Kotaku originally published:
Plaintiffs accuse Warner Bros and 5th Cell of including, without any licenses or authorizations, the Keyboard Cat and Nyan Cat characters in their original Scribblenauts videogame released in 2009, the 2010 Super Scribblenauts, 2011 Scribblenauts Remix, and the 2012 Scribblenauts Unlimited. Defendants are accused of shamelessly using identifying “Nyan Cat” and “Keyboard Cat” by name to promote and market their games. Plaintiffs claim that Warner Bros and 5th Cell’s trademark infringement was willful and intentional and are requesting an award of treble damages and requesting the case be deemed exception under 15 U.S.C. § 1117(a), thereby entitling Plaintiffs to an award of reasonable attorneys’ fees.
So, basically, Schmidt and Torres claim that their content has been used without their authorization, and to promote an entire line of games.
As some have pointed out already, there's a good chance that this lawsuit may not go very far, since both Keyboard Cat and Nyan Cat were trademarked in 2010, and the original Scribblenauts came out in 2009.
Also, most people believe that the lawsuit is both frivolously and laughable, and cast both creators in a fairly negative light. Both memes are no longer hot, and it could be viewed that this is some last ditch effort of Schmidt and Torres to get every last dime from their creations.
Schmidt in particular has rubbed a few folks the wrong way, due some polarizing interactions with internet denizens over the years. His attempt at recreating the same magic with another cat (the original Keyboard Cat, real name Fatso, died in 2000) also led to many people to roll their eyes.
Though, as others have pointed out, both creators are simply protecting their intellectual property, and suing parties for such offenses is something Warner Bros, and other large companies, have long been doing. So this is just an instance in which the roles have been revered, and you have small guys going after the big ones.
But does this also highlight how silly such litigation is in the first place? Perhaps. It's also worth considering the intent of the creators of the game, 5th Cell. Were they trying to maliciously take advantage of the plaintiffs? Or were they simply having fun, perhaps even paying tribute to them, by including both creations that had effectively turned into (at the time) pop culture phenominas?
It's also worth noting how both Keyboard and Nyan Cats are the only internet gags that are in the game. And the answer is, of course not. Though how that fact holds up in court remains to be seen (again, if it even gets that far).