Mobile carriers aren't the only ones guilty of inducing "bill shock," or unexpected charges; the Smurfs are too.

Capcom Interactive, creator of the Farmville-inspired Smurfs' Village app for iOS, has agreed to post a warning about unexpected in-app fees after parents discovered that their children were racking up huge credit card fees while playing the game.

Apparently Smurfberries, the game's currency, cost real-life dollars, and can be purchased with a couple taps. Priced by containers, a "bucket of Smurfberries" costs $4.99, a bushel costs $11.99, a barrel goes for $29.99, and a wheelbarrow will set you back $59.99.

Over at the Apple support forum last month, one parent complained that the app charged his credit card for a wheelbarrow, apparently while his daughter was playing the game.

"I asked her to show me how she did it, and there is no request for iTunes password at any stage in the process. She could have just kept hitting the buy key," he said.

"I am sitting next to [my son] on the couch playing the game," wrote another consumer. "The buy button popped up and he tapped it before I even had the chance to stop him. Does anyone have a number that I can call to see if I can get rid of the charges? Deleting app now."

Capcom responded by publishing this warning in the game's description, "PLEASE NOTE: Smurf Village is free to play, but charges real money for additional in-app content. You may lock out the ability to purchase in-app content by adjusting your device's settings."

Smurfs' Village launched in early November in anticipation of next year's Smurfs 3-D film and briefly overtook Angry Birds as the highest-grossing app on iTunes, according to Gamasutra. It is now the third-highest grossing iPhone app.