O-mouthed - You’re so confused you look like a chicken that just saw a g

You’re so confused you look like a chicken that just saw a ghost.

I walked in on my mom and her coworker eating cereal at 2 a. m. I was O-mouthed.

My teacher told me I failed the test. I was O-mouthed. I thought I aced it.

I saw my dad wearing a dress. I was O-mouthed.