Walnut Creek, Calif. — Cartoonist Troy Walker created a comic strip in 1991 about a sponge with a personality.

Bob Spongee had eyes, legs and arms. He lived on Apple Street with his wife, Linda, and their daughter, Bubbles.

Walker, of Fairfield, Calif., then produced 1,000 dolls: yellow sponges with a "drawn-on" face that he sold as collectibles in flea markets and through the mail.

In 2002, he learned about Nickelodeon's buck-toothed animated character, "SpongeBob SquarePants," who lives underwater in the fictitious city of Bikini Bottom.

"They took all of it," Walker said this week. "I sold the Bob Spongees all throughout Northern California. It obviously fell into the hands of one of the producers of the show. It's a clear pattern of duplication."

SpongeBob's image now decorates almost any object children use - from lunch boxes and sippy cups to pillow cases and window curtains.

The 40-year-old cartoonist has filed a lawsuit in U.S. District Court in San Francisco against Nickelodeon, Viacom, Paramount Studios and Stephen Hillenberg, the creator of SpongeBob SquarePants.

Walker has demanded $1.6 billion in damages, alleging that the defendants used his idea without his permission.

Hillenberg could not be reached for comment. Nickelodeon will not comment on pending litigation, a spokeswoman said in a written statement.

"However we believe this is a baseless claim," the statement says.

Walker originally filed his complaint in August acting as his own attorney. Now the San Francisco-based law firm Nevin & Absalom has taken his case. Walker's attorney, Edward Nevin, was not available to comment.

Walker's complaint lays out Bob Spongee's evolution during the recession of the early 1990s. In Walker's original concept, he drew a nose and mouth on a kitchen sponge, attached plastic googly eyes and placed the effigy in a clear bag that included a small comic strip, "Sponge for hire! Meet Bob Spongee, The Unemployed Sponge."

He said he has kept copies of the advertisements he ran for the Bob Spongee doll in the Oakland Tribune.

He cites a 2004 episode of "SpongeBob SquarePants," called, "Sponge for hire!" as a piece of "undeniable proof" that Nickelodeon ripped him off.

"It is more than ironic that two working-class sponges are named Bob," Walker says in his complaint. "Both characters are unemployed. Both characters live in a house concept."

Walker said he tried to work out a settlement with Viacom's attorneys when he first learned about SpongeBob. But Viacom stopped corresponding with him, he said.

Viacom's attorneys have said in court documents that Sponge Bob is different than Bob Spongee.

"Defendants' work(s) are not substantially similar to any protectible elements of any of plaintiff's allegedly infringed works," attorneys wrote in response to Walker's complaint.