Lemon of Troy

Literally 'legs up', used to describe something turned upside down or a situation thrown into disorder. Not guessable from the individual words because the image does not map to the English idiom.

A fixed reflexive verb used to describe self-congratulatory behavior. Slightly formal in feel but appears in everyday speech; the reflexive construction is obligatory and not negotiable.

A common informal threat or boast. 'Trasero' (backside, rear) softens what in other registers would be a cruder body part. Used freely between children and adults in casual contexts.