Mark isn't especially musical, but he enjoys singing in the car with his family, generally very loudly and not exactly on-key. Mindless repetition of "She'll Be Coming 'Round the Mountain," each verse varying slightly in Level of Ridiculousness, is a particular favorite.
~Does he like to go outside?
Absolutely. Mark is definitely an outdoors person. He's also an indoors person, too, and like all his siblings has an innate love of reading.
~Is he naturally curious?
Is Sir Percy the Scarlet Pimpernel?
~Right, or left handed?
Well, his favorite shirt (the one he wears four or five days out of the week in summer until it is forcibly removed by a sister and put in the washing machine) happens to be red (or at least it used to be red) so we'll go with red.
~Where is he from?
Born and bred in Cedar Lake, Michigan and has lived there all his life.
Mark doesn't really have enemies, per se, though there are a few people he really doesn't like. Frank Whittaker currently tops the list.
“Who wants to make a good impression on a humanoid magazine cover like that,” Mark snorted, and Sylvia choked back a snort of her own. “I bet he spends his whole day practicing how to ask girls out in front of his bathroom mirror. When he’s not applying an entire bottle of hair oil, that is. I bet he wears aftershave just so he’ll smell older.”
He's argumentative but good-natured, enjoys doing things he's been expressly told not to do (sisters aren't parents, after all, and Celia isn't the boss of him) but is generally trustworthy, has never broken a bone in any of the times he's taken a plunge off his bike and has memorized all the kings of Judah both in chronological order and in a personal list ranking them from Most Wicked to Least Wicked.
~What kinds of things get on his nerves?
People nagging him or telling him what to do, wearing a tie, wearing a suit, wearing a carnation in his buttonhole and being a groomsman.
~Is he independent, or needs others to help out?
I'm gonna let you decide that one for yourself, based on the other answers. :D