I see this kind of construction a lot. It usually appears in contexts where a person remarks on something unexpected happening. The pictured example is Goku after surprising everyone with his first kamehameha. The other day, one of my child students put his regular pencil into his coloured pencil box and proclaimed 「入った！」and burst out laughing.
Is there a similarly concise way of expressing this in English that you know of? Am I right in thinking that this phrasing is used to express surprise?
by it_ribbits