This Saturday, May 4, is Free Comic Book Day, an annual orgy of illustrative art in which fair-weather fans descend upon stores to snatch up piles of complimentary comic books. If you’re a true lover of “sequential art” (as comic book genius Scott McCloud calls it), you might want to extend the holiday and head over to Guild Cinema on Sunday, May 5. Local word-and-picture publishing organization 7000 B.C. is sponsoring a special movie screening at 1 p.m. only. The documentary Dear Mr. Watterson looks into the life and art of “Calvin & Hobbes” creator Bill Watterson.