Via Wikipedia:

“Skippy” was first used as a trademark for peanut butter by the Rosefield Packing Co., Ltd., of Alameda, California, in 1933. Percy Crosby, creator of the “Skippy” comic strip, had the trademark invalidated in 1934, but Rosefield persisted after Crosby was committed to an insane asylum, and its successor companies, most recently Unilever, have been granted rights to the trademark over the objection of Crosby’s heirs. There has been much litigation on this point over the decades, some of which remains in progress.[1]

And from The Associated Press:

The Associated Press
Monday, April 5, 2004; 4:59 PM

ANNANDALE, Va. – For nearly 40 years Joan Crosby Tibbetts has waged a one-woman campaign against the makers of Skippy peanut butter, claiming the name was stolen from her father’s popular Depression-era comic strip.

On Monday, Tibbetts’ legal battle ended when the U.S. Supreme Court refused to hear her suit against Skippy’s manufacturer, a division of the multinational conglomerate Unilever. But Tibbetts, 71, said she’ll continue her battle in the court of public opinion.

“This case involves a very important principle … ‘Thou shalt not steal,’” Tibbetts said Monday. “If this case is allowed to disappear and they succeed in shutting me up, who has won? These big corporations that believe they can just wear others down.”

Tibbetts’ crusade began in 1965 when the state of New York tasked her with administering her father Percy Crosby’s estate. She had not seen her father since 1939, when Crosby’s wife divorced him and took the children.

Crosby died in December 1964, after spending the last 18 years of his life in a mental hospital, his cartoon character by then largely forgotten…

Her research led her to the conclusion that the trademark for Skippy peanut butter had been improperly obtained by the Rosefield Packing Co.

She has waged her campaign ever since, a few episodes of success interspersed with endless legal wrangling and frustration.

In 1978 she won a $25,000 settlement from Bestfoods, which had purchased Skippy peanut butter from Rosefield. But Tibbetts said the settlement was with the understanding that Bestfoods would use the original Skippy character in its marketing, which never occurred.

It was also before Tibbetts found documents that she says prove Skippy’s manufacturers knowingly obtained their trademark by fraud and covered up the evidence. One document written by lawyers in 1954 as Bestfoods prepared to buy Rosefield suggested that Bestfoods’ chief counsel should deny knowledge that the Skippy mark had been fraudulently obtained.

Another victory for Tibbetts, of Annandale, Va., came in 2000 when a federal appeals court overturned a ruling that had barred Tibbetts from claiming on the Internet that she was the legitimate holder of the Skippy trademark.

That ruling, on First Amendment grounds, allows Tibbetts to continue her campaign, telling her story on the Internet and agitating for change and advocating a boycott of Unilever products. And now that her civil claim has been denied, she plans to petition the Justice Department for a criminal case.

She acknowledges crusade’s toll – financially, emotionally and physically. She also has been subject to nasty e-mail comments, including one writer who hoped she drowns in a giant vat of peanut butter.

A spokeswoman for Unilever, which has previously said Tibbetts’ claims are without merit, did not immediately respond to a call seeking comment.

And just so we don’t leave you with a good taste in your mouth, a Skippy peanut butter television commercial from the 1950′s (caution, the ad may be a tad bit sexist):