The Defenders and Piranha 3D actor will play Herman Munster in NBC's modern-day reimagining of classic sitcom The Munsters, according to TVLine.
O'Connell joins Eddie Izzard - who was first to be cast as family patriarch Grandpa - on the programme. Spy Kids 4 star Mason Cook has also joined the pilot in the role of Eddie Munster.
Izzard - who is also attached to the pilot as a producer - has promised that in marked contrast to the original sitcom, Mockingbird Lane will be "way darker than people expect".
Pushing Daisies creator Bryan Fuller will write Mockingbird Lane's pilot script, while Bryan Singer (X-Men, Superman Returns) is attached to direct the one-hour show.
Production on the pilot, which has been in development since September 2010, was reportedly delayed earlier in the year.
The original Munsters series starred Fred Gwynne, Al Lewis and Butch Patrick and ran on CBS from September 1964 to May 1966. A sequel series titled The Munsters Today aired between October 1988 and May 1991.