O-mouthed - You look like a frog that just got hit by a truck when you'r

You look like a frog that just got hit by a truck when you're totally shocked.

I saw my uncle wearing a tutu at the office party. I was O-mouthed.

I got a 100 on a test I didn’t study for. I was O-mouthed.

I walked in on my brother and his pet turtle. I was O-mouthed.