Something in Jim's post of October 14 2009 (wow, seems like yesterday!) caught my eye "...Even two-engine fighters, Lightnings and Black Widows (P-61s), were modified."
Now from what I know P-61s were heavy, if not the heaviest fighters of WW2, weighing in at around 25 000 pounds when empty and I was wondering if any attempts were indeed made to catapult-launch them off carriers.
The answer is to be found on page 112 of "Northrop's Night Fighter - The P-61 Black Widow" by Jeff Kolln. According to the book, two P-61s were loaned to the Navy for testing the feasibility of catapult-delivering the aircraft type to Pacific bases by aircraft carrier. Around 50 test-launches by H2 hydraulic catapults were successfully performed during the latter half of 1944 at NAS Mustin Field, Pennsylvania. Test-launches by catapult off an escort carrier were also successfully conducted, which "certified" the P-61 as a catapult-capable aircraft, although there is no evidence that this method of delivery was ever actually used.