back story: We're "those parents," who prefer not to have the girls drinking soda, eating sugary cereal, snacking on candy. So "treats" become small glasses of juice or chocolate milk. The girls are like all kids, wanting treats. L has a huge sweet tooth (my genes I think). Luckily L is also a good breakfast eater, K, not so much so....
At the breakfast table:
K: I want something.... I want a special treat!
M: K, you need to eat something nutritious for breakfast.
K: But I want a treat!
L (pushing aside her previously satisfactory oatmeal): I want a tweet!
M: After you eat breakfast.
me: You already had some chocolate milk.
K: But I...
L: I want a tweet!!
M&me: After you have some breakfast!
K (obviously frustrated): That's your deal!
M & I looked at each other and started laughing. She's right, it is our deal. I have no idea where she got that phrase from though, and in this context it just gave us the giggles.