(idiomatic, humorous) Used to express surprise about someone's uncharacteristic or wacky, offbeat past actions.

Inquires about the subject's current occupation.

Used to ask what the interlocutor is currently doing.

(US, colloquial, often preceded by hey) Used to express surprise or dissatisfaction with an action or statement of another person, especially to that person.

Events that have already taken place cannot be changed and actions that have already been committed cannot be undone, so it is best not to dwell on them.

(dated) whatchamacallit

(dated) Synonym of know what is what

(rhetorical question, somewhat hostile) Expresses discomfort because the interlocutor is looking at something; usually, this is said when the interlocutor has been staring at the speaker.

(MLE, MTE, slang) what's up, what's happening (a greeting)

(informal) Synonym of what's your poison