Those totally delightful sheep who appeared earlier in a jeep (1986) and on a ship (1989) turn up in a country store, impecunious but in need of supplies for a birthday picnic. No problem: ``Sheep blink. Sheep think. What can they swap to pay the shop? Sheep clip wool, three bags full.'' Again, Apple's warmly comic illustrations are the perfect complement to Shaw's exquisitely concise wordplay. (Picture book. 2-7)