We're going through a phase here (PLEASE LET IT BE JUST A PHASE) where food is something of a struggle. To be more specific, Will and Emma like opposite foods.
I honestly don't think they do it on purpose because it isn't that obvious; the more I think about it, the more ridiculous it seems.
Right now, the foods that Emma refuses to eat are the ones Will would eat exclusively: toast, bagels, German pancakes, quesadillas, cinnamon/orange rolls. For the life of me, I can't figure out why she won't eat cinnamon or orange rolls.
The foods that Emma asks for are the ones that Will needs persuading to eat. (In some cases, he won't touch them no matter the method of persuasion.) Spaghettios, stew on rice, soup, string cheese, oatmeal, alllllll the yogurt. Most cooked vegetables and anything with multiple foods touching each other, like all the best foods in the world.
They're both obsessed with blueberries but won't try fried eggs or, heaven forbid, noodles with SAUCE on them. Will hates potatoes in every form. Lex eats anything and everything I give her, which makes me love her even more.
(Until I remember that both my older two were that way in the beginning ...)