A bizarre series of fast-food restaurant commercials starring a disembodied, talking head named Bob is getting raves from the advertising industry.

But some parents have complained to the Krystal Co. that Bob is appearing offscreen in their children's nightmares.Krystal, known for its tiny Krystal hamburger, has 236 restaurants in Alabama, Florida, Georgia, Mississippi and Tennessee. All but four are operated by the company, making Krystal the nation's largest privately owned restaurant chain.

In the TV ads, Bob the talking head extols the virtues of the restaurant chain while perched in a variety of locales, including a pickup truck bed, a front lawn, a henhouse and a Krystal grill.

The commercials end with the tagline: "Head to Krystal."

Advertising Age magazine gives the new television ad campaign, developed by Bloom FCA of Dallas, three out of a possible four stars in its current issue.

"It's all very bizarre and . . . marginally offensive," Bob Garfield wrote in Advertising Age. "But the outlandishness is sure to capture the imagination of the teen-age target audience."

But Krystal officials report some parents have complained that the campaign, which began airing earlier this month in some markets, is frightening their children.