Mom's Friend's Son -- The son of your mom's friend that your mom constantly compares you to, because he is always superior to you in virtually everything. With an expression of disappointment, your mom always asks you why you can't be like him.
Me: I'll clean my room later. Let me finish watching the basketball game.
Mom: name of MFS
's mom told me that his room is always clean. Why can't you be like him, huh? Why??
MFS: I just got my exam back today.
Me: What did you get.
MFS: Ehh, not as well as I wanted to do.
Me: So what was your score??
MFS: .. 91.
Me: Dang! What an MFS!