The phrase 'Johnny On the Spot' refers to a person who is always available, ready, reliable and willing to perform a duty or a task without delay.
Example of use: "when Gabriel comes over, you need to be my Johnny on the Spot and make sure that we have whatever he needs."
Interesting fact about Johnny On the Spot
The phrase 'Johnny on the Spot' was first recorded is in the 1896 April issue of the New York Sun: "JOHNNY ON THE SPOT: A New Phrase Which Has Become Popular in New York." The origin of the phrase can't be traced specifically, though it certainly originated from the expression ‘Johnny is always on the spot when wanted.’
