"Y de vez en cuando, alguna película."
"some movies" would be "algunas películas"
It's not a very complete sentence, but it is just an exercise.
"A movie" would be a more common way of saying it in English, but I still think it's valid. For example, a more complete sentence might be...
"We usually watch TV, and once in a while, some movie."
By saying "some movie" makes it sound a little more vague, like the choice is somewhat abritrary or you are being coy about your choice of movie, whereas "a movie" is more neutral.
It's really unusual in this sentence but I don't think it's incorrect. "What are you watching?" "I don't know, some movie." Maybe this sentence could be last on a list of things to do with another person.
"We'll go out to eat, to dance, to ride around. We'll see plays and concerts..."
"I like movies."
"And once in a while, some movie."
In the last prompt which I answered "seems like she has few friends" was wrong, according to the logic that I left out "IT seems like she has few friends." Yet you can imagine an English speaker saying "seems like she has few friends," leaving out the It. Yet now this sentence, "and now and then, some movie" makes almost no sense in English and would rarely be said... why isn't this sentence "And once in a while, we watch some movies"? I'm irritated by how these constructed sentences are inconsistent and oftentimes bizarre, while the "grading" of whether you answer them correctly is sometimes extremely strict.
I look at it this way: even if I know the sentence translated is wrong and I lose a heart, doing the lesson over again only reinforces it. Once in awhile, I will comment. The second time through, I just ensure that I put what the owl wants :) Have fun with it; that is what learning is supposed to be about.