An image of a farting unicorn is causing a stink between a Colorado artist and Elon Musk.

Tom Edwards created the whimsical image of a unicorn powering an electric car with its own gas in 2010, and put it on ceramic mugs that he sells. “Electric cars are good for the environment because electricity comes from magic,” the mugs say.

That eventually caught the eye of Musk, the chief executive of electric-car maker Tesla Inc. TSLA, +3.75% , who tweeted last year: “Maybe my favorite mug ever.”

A month later, Musk tweeted a picture of the very same farting unicorn that appeared as a doodle, apparently drawn on a sketch pad found on Tesla’s center console.

The farting unicorn also appeared as an app icon on the Tesla console screen, and again appeared on Tesla’s annual Christmas card last year.

Edwards’ lawyers got involved in May, claiming Tesla’s appropriation of the farting unicorn was a clear copyright infringement. “Please don’t take this as a shakedown,” Denver attorney Timothy Atkinson wrote to Tesla, according to a report by Denver-based alt-weekly Westworld. “What we are seeking instead is a discussion, and a mutual decision in a way to value the past and continuing use of the image, in a way that both sides can feel good about.”

Edwards told The Guardian that he’s not seeking a ton of money. “I love the fact that it’s in the cars, but I just want them to do the right thing and pay me adequately for it,” he said. “Elon Musk can be a hero for standing up for artists’ rights.”

That seems less unlikely now. On Tuesday, Edwards’ daughter tweeted: “hey y’all Grimes’ boyfriend ripped off my dad’s art! this is a true story! what do you have to say for yourself @elonmusk ??”

Musk responded: “We gained no financial benefit. Have asked my team to use a diff example going forward. He can sue for money if he wants, but that’s kinda lame. If anything, this attention increased his mug sales.”

Still, Edwards said he hopes for an amicable resolution. “I’d really like to get on Elon Musk’s good side … He’s really really interesting. But he isn’t above copyright law,” he told The Guardian.

Tesla had no comment, a spokesperson said.