ˌJohnny-on-the-ˈspot noun [singular]
informal someone who immediately offers to help, takes an opportunity etc

[TahlilGaran] Dictionary of Contemporary English ▲

Johnny-on-the-spot
[American, informal]
someone who is immediately ready to do something, especially to help someone.
This guy had just gotten a flat tire, and there I was, Johnny-on-the-spot with my tools in the back of the car.

[TahlilGaran] English Idioms Dictionary ▲

Johnny-on-the-spot
someone who is at the right place when needed or is right on time
He is always Johnny-on-the-spot. Just when we need him he arrives.

[TahlilGaran] English Idioms Dictionary ▲

johnny on the spot
adj. phr. At the right place when needed; present and ready to help; very prompt; on time.
A good waterboy is always Johnny-on-the-spot.
The firemen were Johnny-on-the-spot and put out the fire in the house soon after it started.
Compare: ON THE JOB.

[TahlilGaran] English Idioms Dictionary ▲