In a world where everyone wants to go to Mars, Amazon and Blue Origin chief Jeff Bezos is eyeing the moon. And Tesla and SpaceX CEO Elon Musk has something to say about it.

Speaking at a press event on Thursday, Bezos unveiled his company's first lunar lander, called Blue Moon. The lander comes with a decidedly moon-like design and is designed to bring astronauts to the moon by 2024.

Alongside the Blue Moon, Bezos showcased the BE-7 rocket engine, which aims at taking folks to the moon in the future. Ultimately, Bezos believes there's a real opportunity for Blue Origin and humanity on the moon.

It didn't take long for Elon Musk to respond with a rather graphic response.

He took an image of a news article about the Blue Origin plan on Thursday and scrubbed out the "Moon" next to blue. He replaced it with balls to read "Blue Balls."

"Oh stop teasing, Jeff," Musk said in the caption to the tweet.

Soon after, the tweet went viral and once again, the Tesla chief's tweeting practices were called into question. Musk was earlier targeted by the SEC for tweeting about a possible plan to take Tesla private. He didn't do it, but it impacted the company's shares. Musk and the SEC have had more disagreements since then and have agreed to a truce.

Still, that agreement doesn't stop Musk from using his account to tweet criticisms to his more than 26 million followers. And the jab at Blue Origin is just the latest in a string of criticisms he's leveled against the Bezos company.

Last year, Musk notably called Bezos a "copycat" after Blue Origin said it would send satellites into space. He's also scoffed at some of Blue Origin's plans.

But the latest tweet is the most direct -- and lewd -- Musk has been in criticizing Blue Origin in recent memory.

The move doesn't seem to make much sense. It could all be in fun, I suppose, but Bezos and Musk seem like they both are on the same page with a plan to go to space and change space travel. Criticizing Bezos in that way doesn't necessarily serve Musk well.

Alas, that might not both Musk. He's comfortable using his Twitter account to trade shots with nearly everyone. And considering all the attention Blue Origin's announcement was given on Thursday, it seemed like an obvious target.

Jeff Bezos hasn't yet responded to the Musk tweet.