Had some conversations about these lately and realized they're hard to adequately describe for someone who's unfamiliar with them -- or just essentially averse to Norman Rockwell's work in general, which seems fairly common -- but say whatever you would about what Rockwell's come to represent, I think these picture-puzzle indulgences are a lot of fun. Here's a couple examples.
April Fool's Day 1943 (image c/o eCrater):
April Fool's Day 1948 (image c/o Global Gallery): Following are all the "wrong-things" Rockwell cited for publisher in the 1948 installment directly above:
1) two different moldings on cupboard, 2) woodpecker head on crane's body, 3) coffeepot's spout is upside down, 4) barbed wire instead of clothesline, 5) insignia is on back of fireman's helmet instead of front, 6) green and red lights reversed on ship's lantern, 7) beast crouched on upper shelf, 8) cup not hanging by handle, 9) electric bulbs growing on plant, 10) the girl's head on sculptural bust, 11) rat's tail on chipmunk, 12) pen with pencil eraser, 13) top of brass vase suspended, 14) face in clock, 15) candle where kerosene lamp should be, 16) sampler dated 1216, 17) Winter seen through left window, Summer through right, 18) antique dealer's head on dolls, 19) nine branches on traditional seven-branch candelabrum, 20) girl's hair in pigtail on one side, loose on other, 21) titles on books vertical instead of horizontal, 22) girl's sweater buttoned wrong way, 23) mouthpiece on both ends of phone, 24) phone not connected, 25) goat's head with deer's antlers, 26) no shelf under books, 27) lace cuff on man's shirt, 28) five fingers and thumb on girl's hand, 29) gun barrel in wrong place, 30) saddle on animal, 31) potted plant on lit stove, 32) girl's purse is a book, 33) only half a strap on girl's purse, 34) skunk in girl's arms, 35) sea gull with crane's legs, 36) stovepipe missing, 37) Mona Lisa has halo, 38) Mona Lisa facing wrong way, 39) Abraham Lincoln with General Grant's military coat, 40) stove has "April Fool" on it, 41) hoofs instead of feet on doll, 42) little girl sitting on nothing, 43) Rogers group is combination of soldier from Our Hero and girl from "Blushing Bride," 44) brass kettle has two spouts, 45) spur on antique dealer's shoe, 46) mouse and ground mole conferring, 47) ground mole's tracks in wooden floor, 48) dog's head on cat's body, 49) raccoon's tail on cat's body, 50) ball fringe standing straight up at angle, 51) stove is missing one leg, 52) two kinds of floor, 53) signature reversed, 54) last name spelled wrong, 55) flowers growing in floor, 56) girl's shoes & socks don't match.