Mark Pett, creator of Lucky Cow holds the Guinness World Record for the LARGEST comic strip. Back in June of 2003, he organized a fund-raising event for the local high school art department wherein students recreated a larger scale version of a Lucky Cow strip. As far as I know, that record still stands. You can read more about the making of the strip over at Mark’s web site.
According to E&P, a group of students over in Dundee, Scotland are attempting to to create the LONGEST comic strip measuring 974 feet long. The earlier record was set by Walt Disney at 787 feet long.