Really common conversation these days.

Elizabeth: Parker, I'm eating Chex cereal just like you!

Parker: Yes, Snizabeth. I know that. Don't tell me things I already know.


Another example...

Miranda: Mom said to go get dressed, Parker.

Parker: I know that Snanda.


Apparently the use of SN before the name is to indicate that they said something he already knows.

I crack up each time.