Look at this nasty passage (that begins in the third line and gets repeated) in the key of B major from Mendelssohn's incidental music for his pocket version of A Midsummer Night's Dream. Nobody writes exposed passages like this for the viola in truly viola-unfriendly key of B major. After tearing out some hair and fighting with scales and double stops in B major for a while, I finally realized that this passage is a variation on the "Bottom" theme (i.e. the donkey). In order to give it that certain donkey-esque je ne sais quois, Mendelssohn gave it to us, in this key, and in this register. Now there's a smart composer. And one with a sense of humor. It takes a sense of humor to play it too.