A person who is on hand and ready to perform a service or respond to an emergency; An unusually alert fellow who is capable of decisive action, seizing an opportunity.
When you need help, call me and I will be your Johnny-on-the-spot" "Oooh, thank you, girl!
by GJ's April 06, 2011
The act of shitting on the sunroof of a car, which results in fecal matter splattered on the driver's head/face upon opening the sunroof.
I climbed up on Meredith's car and left her a little johnny on the spot before she left this morning.
by "Jim Douche"/Erik Higbie August 19, 2009