小题大作 (source) means to make a mountain out of a molehill.

According to my little "New Edition Chengyu Dictionary" (新编成语词典), the phrase first appeared in the Ming-Qing dynasties period. On the imperial examination in that period, there were straightforward questions covering the Four Books of philosophy that were called "小题" ("little questions") and more involved questions on the Five Classics of Confucian philosophy that were called "大题" ("big questions"). Examinees who used composition methods meant for the "big questions" on the "small questions" were said to have commited 小题大作; that is, to have written weighty essays on trite subjects. The example sentence given is: 这本来是件很容易解决的事，你又何必小题大作，大闹一番呢?, or "This was supposed to be an easy problem to solve; what need was there for you to raise such a ruckus making a mountain out of a mole hill?"

Thank you Selina, Hebe, and Ella (S.H.E.), for teaching us about the Chinese classics!

(Also, notice the line in the song "来一点嘻哈" and refer to my last post. Aren't we glad it's not something boring like ヒップホップ? That, my friends, is why I switched from Japanese to Chinese.)