This miniature miser lives at Fablehaven. He has a bristly auburn beard, a knobby nose, and speaks with an Irish brogue. He wears a red frock coat and an outdated hat. He can be caught, but never the same trap twice.
The Journal of Secrets explains that there is a magical pond somewhere on Fablehaven where a treasure hunter can capture a Leprechaun.
In book 5, Seth recieves a letter from Patton and it says that he [Seth] has to catch him [Cormac].