On Tuesday, Denver’s alternative newspaper Westword reported that Elon Musk had stolen a drawing of a farting unicorn from a Colorado artist named Tom Edwards. After Edwards’ daughter tweeted about it, Musk jumped in to say that suing him for stealing her dad’s artwork would be totally “lame.” By now it’d be hard to tell that Musk thought that an artist defending himself against theft was lame, however, because the billionaire has scrubbed his Twitter of every mention of the farting unicorn.

The farting unicorn in question was originally produced by Edwards in 2010 for a mug about electric cars. On the mug, a unicorn flanked by smiley faces and a rainbow is seen farting into the exhaust pipe of a car. Opposite the unicorn, the mug reads: “Electric cars are good for the environment because electricity comes from magic!” According to Edwards’ blog post about the mug, he was inspired to make it after reading a “dismal” article about fracking, the process of extracting natural gas from the Earth.

In a now-deleted tweet from February 2017, Musk tweeted a photo of Edwards’ mug and said it was “maybe my favorite mug ever.” Edwards told Westword he was pretty happy about the publicity generated by Musk’s tweet because it led to a bump in mug sales. Then, only a month later, Musk tweeted out a facsimile of Edwards’ farting unicorn to demonstrate the “sketch pad” feature that comes installed in every Tesla.

Shortly thereafter, Edwards learned that the farting unicorn was also used as a small icon on Teslas’ dashboards and that the company had also used it in a Christmas card.

“It’s part of their branding now,” Edwards told Westword. “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.”

On May 23, Edwards’ lawyer sent a letter to Tesla. He didn’t ask the company to stop using the image, but said it was an “invitation for all parties to continue to benefit from the whimsical, and amazingly spot on piece of imagery my client created in 2010, which now appropriately finds a home in the operating system of the magical vehicles your company produces.” According to Edwards, he hasn’t received a response from Tesla yet.

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On Tuesday, Edwards’ daughter Lisa Prank tweeted out the Westword article, saying “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 hopped into Prank’s mentions and said the image was “chosen randomly by software team as a joke (they didn’t tell me in advance)” and offered to “change it to something else if your Dad wants.” Prank responded saying “Your company has been using his creative property for a year without credit or compensation—don’t you think artists deserve to be paid for their work? May you can respond to the letter his lawyer sent you and you guys can work something out.”

Musk replied by saying the drawing used in Tesla’s is “actually someone else’s drawing.”

“He can sue for money if he wants, but that’s kinda lame,” Musk replied in a now deleted tweet. “If anything, this attention increased his mug sales.”

After the Guardian published a story about the internet beef, Musk again tweeted at Prank, saying he “popularized” the mug “for free.”