The frenemyship between OpenAI CEO Sam Altman and Elon Musk just got a little spicier.

Last week, the Tesla CEO announced xAI’s new project, “Grok,” a ChatGPT rival that infuses crass humor and is trained on recent posts on X, the company formerly known as Twitter.

Altman on Thursday night posted a screenshot of the latest version of OpenAI’s platform, which now allows you to create customized versions of ChatGPT called GPTs.

In his version, he instructs it:

Be a chatbot that answers questions with cringey boomer humor in an awkward shock-to-get-laughs sort of way.

ChatGPT Builder replies:

Great, the chatbot is set up! Its name is Grok. How do you like the name, or would you prefer something else?

GPTs can save a lot of effort: pic.twitter.com/VFIrGzPuMN

— Sam Altman (@sama) November 10, 2023

Ouch.

There’s bad blood between Altman and Musk, once former friends. Musk and Altman, along with others including Peter Thiel, founded OpenAI as a non-profit in 2015, with a goal of advancing open sourced research on artificial intelligence. According to Walter Isaacson’s biography of Musk, Musk was upset when OpenAI, under Altman, transitioned away from a pure non-profit and partnered with Microsoft.

It was also perhaps no coincidence that the announcement of Grok happened just days before OpenAI’s highly-anticipated DevDay event this week, where the custom ChatGPTs were announced.