For the benefit of anybody who doesn't get this reference, Ernest is the name of a character from a series of American commercials, a children's TV show and then a number of films. One of those films is called Ernest Scared Stupid, which is the joke here.
The entire Ernest franchise is kind of a uniquely American phenomenon; they're not particularly well-known outside of North America. I doubt kbin's Ernest is compared or contrasted with TV's Ernest often at all in Poland.