Lobsterfest

Common informal adjective describing someone who is irritable and complains frequently. Used affectionately or teasingly between people who know each other well.

Literally 'little powder keg.' Used informally to describe someone who is energetic to the point of being hard to handle, either in personality or intensity. Can be affectionate or a mild warning.

A playful, impulsive expression suggesting a reckless physical test. The humor comes from the literal idea of something exploding being treated casually.

Though each word is familiar, the phrase is used in Latin American Spanish as a fixed expression of reciprocity. In context it can carry an ironic or humorous tone depending on delivery.