A title is not the most binding straitjacket around. A title might specify a genre or setting, but the story remains wide open. A movie based on a toy might seem silly, but it will only BE silly if the creators make it so.
For a master class on how not to make silly movies, listen to the writers' commentary track on the Pirates of the Caribbean: The Curse of the Black Pearl DVD
Even if you aren't interested in why it was the superior choice to make Commodore Norrington a priggish good guy – but still a good guy – listen to the track anyway. Seriously, how freakin' awesome is it that a movie based on a theme park ride includes a writers' commentary track?!
[I've linked above to the Blu-ray edition. Amazon no longer lists the 2-disc DVD version on which I listened to the commentary track. Anyone know if the Blu-ray version includes the same tracks?]