For international pop star Katy Perry and Australian fashion designer Katie Perry, the answer can be found in a slight variation in spelling and more than six years of litigation.
The fight over the rights to the Katie/Katy Perry name began when the designer - legally known as Katie Taylor - sued the performer behind Firework and Roar for trademark infringement.
The US singer, whose real name is Katheryn Hudson, hit back with a bid to cancel the designer's trademark, arguing it was likely to harm her reputation or deceive shoppers.
The dispute dragged on for over six years after the pop star successfully overturned an initial Federal Court ruling that the designer's trademark had been infringed.
But it came to a decisive end on Wednesday when the nation's highest court decided the David-and-Goliath battle in favour of the Australian.
The designer's mark was not in breach of trademark law and was not likely to harm the Dark Horse singer's reputation or cause confusion, the High Court ruled in a majority decision.
Ms Taylor's lawyers argued during the hearing that shoppers were savvy enough to distinguish between the two spellings and wouldn't connect the label to the pop star.
She claimed she didn't know of the singer's existence when she first sought the clothing trademark in 2007.
But by the time Ms Taylor applied to trademark the name Katie Perry, she had heard I Kissed a Girl on the radio and bought the song on iTunes.
There was no way she could have known how famous Ms Hudson would become, her lawyer told the High Court in September.
But the pop star's lawyers contended Ms Taylor should have made a complaint earlier instead of waiting 10 years after the sale of Katy Perry-branded merchandise began.
The designer faced the possibility of having her designer's mark de-registered after her 2023 win in the Federal Court was overturned on appeal.
The appeal judges found the Katie Perry trademark was deceptively similar to the pop star's brand and was likely to cause confusion.Â
But the appeal judges made a mistake in concluding there were grounds to cancel the trademark, the High Court determined in its majority ruling.
The decision marks the end of a tug-of-war that has been running since 2009, when Ms Hudson became aware the designer had applied to register the Katie Perry trademark.
According to court documents, the superstar told her talent agent Steven Jensen to "keep me outta it entirely".
"I wouldn't have even bothered with this (if) mtv hadn't picked up this silliness," she wrote in an email.
"Dumb b****! Rawr!"
The singer has been ordered to pay Ms Taylor's legal bill, with the figure to be determined at a later date.
The designer has been contacted for comment.
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