Earlier this week, Seattle-based musician Robin Edwards—who records and performs under the moniker Lisa Prank—got into a Twitter feud with Elon Musk over the Tesla head’s alleged copyright infringement of one of her father’s illustrations, which depicts a unicorn farting into a funnel connected to an electric car. Let’s dive in.

In February 2017, Musk tweeted an image of Tom Edwards’ “Farting Unicorn” mug, which features the aforementioned illustration and the following message: “Electric cars are good for the environment because electricity comes from magic.” As Stereogum notes, Musk re-created the image in Tesla’s sketchpad app the following month to demo the functionality. Edwards didn’t mind the recreation until it was made apparent to him that the image was being used as an icon in the interface of every Tesla car, without any compensation.

“I realize my farting unicorn is not as serious as whistleblowers, but honestly, it’s all about integrity,” he told the Guardian. “I’d really like to get on Elon Musk’s good side … he’s really really interesting. But he isn’t above copyright law.”

Which brings us to Lisa Prank, who tweeted at Musk to ask for an explanation. In a since-deleted exchange (Musk has wiped his tweets; Lisa Prank’s are still online), Prank asked him, “Don’t you think artists deserve to be paid for their work?” Musk replied, “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.”

Musk also claimed that he already offered to financially compensate Edwards for his work, a claim that Prank claims is false.

Edwards’ mug is currently out of stock, but you can back-order one here.