Johnny-on-the-spot
One who is available and ready for action. Thankfully, Pat was Johnny-on-the-spot with buckets when the roof started leaking.
Johnny-on-the-spot
A person who is available when needed, as in He always is there at the right time, a real Johnny-on-the-spot. [Late 1800s]
Johnny-on-the-spot
A person who is present at a crucial time. This term comes from nineteenth-century America. An early appearance in print is in George Ade’s Artie (1896): “I could see that a Johnny-on-the-spot . . . was trying to keep cases on her.”