fatuous
Meaning: silly, foolish
Usage: He considers himself a serious poet, but in truth, he only writes fatuous limericks.
inane
Meaning: silly and meaningless
Usage: Some films are so inane that the psychology of the characters makes absolutely no sense.
frivolous
Meaning: of little importance, trifling
Usage: Someday, all that anxiety about whether your zit will disappear before the prom will seem totally frivolous.