“一言既出驷马难追”的英语表达可以有多种，以下是一些搞笑且富有表现力的版本：
A word once spoken cannot be overtaken even by a team of four horses.
What is said cannot be unsaid.
A promise cannot be taken back once it is made.
A word spoken is past recalling.
Once word is uttered, it can't be overtaken even by swift horses.
这些表达都传达了“说出去的话就像泼出去的水，无法收回”的意思，既简洁又形象，适合在需要幽默感的场合使用。你可以根据具体的语境选择合适的表达。