Dim-bulb

In Snow White [and the Seven Dwarfs], [Walt] Disney and his staff met the challenge of creating believable characters. Each of the seven dwarfs, from sober-sided Doc to dim-bulb Dopey, had a distinct personality.

Source: wiktionary

Up to now the guy's just a dim-bulb character who likes to dress up in a sailor suit and spoon creme broolay out of a bowl for a living.

Source: wiktionary

Well, long ago, a man named Aesop met a whole bunch of bossy, silly, funny, annoying, dim-bulb people, and he wanted to do something about it. He decided to write stories about these people, and end each story with a lesson […]

Source: wiktionary

It’s harder to care about someone dying when you actively want them to disappear from the screen. And when the film itself proceeds so straightforwardly, and you know that even [Jennifer Love] Hewitt’s dim-bulb boyfriend (Freddie Prinze Jr.) will survive, much of the fun is lost.

Source: wiktionary