The TV show hasn't been on for some time, actually. Like I said, CN has not so much as run an episode before the run up to the movie's release, only running the same 5 shows in succession all day long (before Adult Swim, of course). An opportunity was lost. Meanwhile, Nicktoons runs KFP and Monsters VS Aliens (despite cancelling it after one season) even more into the ground.
The fact of the matter is, every month but May has been weak for movies. Lego and Captain America were the only ones to really perform well in those months. March failed everyone, not just The Muppets. Heck, Dragons pretty much made what Peabody and Sherman did in 2 weeks. And P&S was probably the most successful of the bunch. Above all, there seems to be a sense of ennui considering there hasn't been a blockbuster film in this month so far. Though there's been "Edge of Tomorrow" which in 2 weeks made barely what Dragons did in its first (why isn't anyone calling THAT a bomb?). Maybe the long winter has kept kids in school over the summer preventing real weekday numbers. Still, there's NO excuse for pulling advertisements for the film (minus the merchandising) after the first week had a modest, but disappointing opening.