A Johnny-on-the-spot is a person who is right there when something needs doing — they offer help at once, or they grab a chance the moment it appears. You might say you needed an extra driver, and luckily someone was Johnny-on-the-spot.

A Johnny-on-the-spot是 is a person who is right there when something needs doing是一個在需要幫忙的時候剛好就在場的人——they offer help at once他們會立刻伸出援手，or they grab a chance the moment it appears或是機會一出現就馬上抓住。You might say you needed an extra driver你可能會說你需要多一個司機，and luckily someone was Johnny-on-the-spot而幸運的是有人正好Johnny-on-the-spot（隨叫隨到）。

It is informal, a bit old-fashioned, and mostly American; younger people may not say it much, though they will still understand it in a story.

It is informal, a bit old-fashioned, and mostly American這是口語、有點過時、主要是美式用法；younger people may not say it much年輕人可能不太常這樣說，though they will still understand it in a story不過在故事裡他們還是聽得懂。

Johnny here is not a real person's name. English has long used Johnny as a stand-in for some fellow, and on the spot means both in that place and at that very moment. Put together, it paints a person who turns up exactly where and when they are useful.

Johnny here is not a real person's name這裡的 Johnny 不是真實人名。English has long used Johnny as a stand-in for some fellow英文長久以來都用 Johnny 來泛指「某個傢伙」，and on the spot means both in that place and at that very moment而 on the spot 同時指「就在那個地方」和「就在那個當下」。Put together合起來，it paints a person who turns up exactly where and when they are useful它描繪出一個剛好在需要的地方、需要的時刻出現的人。

It can sound warm (what a help) or a little teasing (always leaping in). You will also see it written with different hyphens, or with none.

It can sound warm它可能聽起來很溫暖 (what a help)（真是幫了大忙）or a little teasing或是帶點調侃 (always leaping in)（老是搶著跳進來）。You will also see it written with different hyphens你也會看到它用不同的連字號寫法，or with none或完全不用連字號。