It's a wild and crazy market, Steve Martin's voice cautions investors in TV spots from Merrill Lynch & Co.'s private client unit breaking June 15. WPP Group's J. Walter Thompson, New York, continues the "Ask Merrill" tagline started in January, but adds a more direct pitch to investors looking for money management advice. In one spot, suits cruise the aisles in a supermarket where prices fluctuate wildly as they shop. If cereal prices moved like stocks, would shoppers be paralyzed by fear, or "follow the next hot thing?" asks Mr. Martin. Art directors: Marcelo Tuidoli, Troy Scarlett, Glenn Price. Copywriters: Nat Whitte and Howard Lenn.