i seen that - When you see someone acting like a total lunatic, and you're

When you see someone acting like a total lunatic, and you're so confused and annoyed that you can't even talk.

'I seen that!' my friend said when my dog ran around the house like it was on fire.

I said 'I seen that!' when my brother started talking to a wall like it was his best friend.

My mom said 'I seen that!' when my little brother tried to eat a whole cake in one bite.