Is it okay to say Mom's got an "extra-large" anything?!?

I was getting ready a few weeks ago and overheard this from the dining room:

7-year-old (to the 5-year-old): "Yours would be medium, mine would be large, and Mom's would be EXTRA-large"

(at which point I yelled from the other room...)
Me: "Hey! You don't say your mom has an "extra-large" ANYTHING!

7-year-old: "MOM!!!! We're talking about BRAINS!!!"

(I'm starting to think maybe an extra-large mouth is my problem).

Telling Time

I overheard this conversation between the boys recently. I am rarely awake before they are, but it was after 8 am.

4-year-old: (to his brothers) "Can we wake up?"
7-year-old: (to 5-year-old) "Can you go check the time?"
5-year-old: "No." (To 4-year-old) "You go do it."
4-year-old: "But I don't know how to tell the time."
7-year-old: (to 4-year-old) "Just go look and come back and tell us the numbers."
(long pause as 4-year-old comes out to check the clock)
4-year-old: "OH MY GOSH...there's an 8 on the end of it.....MOM! Can we wake up?!"