PHOTO: Chevrolet
Now playing
01:50
Demand for electric cars has grown slowly. But the tsunami is coming
Bitcoin
PHOTO: CNN
Bitcoin
Now playing
03:17
Tesla invests $1.5 billion in bitcoin
PHOTO: CNN
Now playing
03:14
In 2010, Elon Musk had big plans for Tesla. Listen to his predictions
Tesla co-founder and CEO Elon Musk introduces the newly unveiled all-electric battery-powered Tesla Cybertruck at Tesla Design Center in Hawthorne, California on November 21, 2019. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)
PHOTO: FREDERIC J. BROWN/AFP/Getty Images
Tesla co-founder and CEO Elon Musk introduces the newly unveiled all-electric battery-powered Tesla Cybertruck at Tesla Design Center in Hawthorne, California on November 21, 2019. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)
Now playing
02:01
Elon Musk has a lot to say about Covid-19. Some of it isn't true
Tesla Cybertruck
PHOTO: Tesla
Tesla Cybertruck
Now playing
01:36
Watch the Tesla Cybertruck's unbreakable windows break
Brussels, Belgium, Jan 18, 2019: metallic red Tesla Model 3 and blue Tesla model X at Brussels Motor Show.
PHOTO: Grzegorz Czapski/Shutterstock
Brussels, Belgium, Jan 18, 2019: metallic red Tesla Model 3 and blue Tesla model X at Brussels Motor Show.
Now playing
03:33
Analyst: We see good things happening with Tesla
Now playing
01:09
Elon Musk busts a move in Shanghai
PHOTO: Gabe Ramirez/CNN
Now playing
01:19
See Tesla's new Model Y
Now playing
01:53
How Tesla made electric cars sexy
PHOTO: Sean R Clark/CNN
Now playing
03:16
Tesla's Model 3 is a top seller. But it's not the electric car for everyone
PHOTO: Bloomberg/Getty Images
Now playing
03:21
Hear some of Elon Musk's most ambitious predictions
CHICAGO, IL - JUNE 14: Engineer and tech entrepreneur Elon Musk of The Boring Company listens as Chicago Mayor Rahm Emanuel talks about constructing a high speed transit tunnel at Block 37 during a news conference on June 14, 2018 in Chicago, Illinois. Musk said he could create a 16-passenger vehicle to operate on a high-speed rail system that could get travelers to and from downtown Chicago and O
PHOTO: Joshua Lott/Getty Images North America/Getty Images
CHICAGO, IL - JUNE 14: Engineer and tech entrepreneur Elon Musk of The Boring Company listens as Chicago Mayor Rahm Emanuel talks about constructing a high speed transit tunnel at Block 37 during a news conference on June 14, 2018 in Chicago, Illinois. Musk said he could create a 16-passenger vehicle to operate on a high-speed rail system that could get travelers to and from downtown Chicago and O'hare International Airport under twenty minutes, at speeds of over 100 miles per hour. (Photo by Joshua Lott/Getty Images)
Now playing
00:53
Musk opens up about Tesla's near 'death'
Now playing
01:04
Hear Elon Musk's bold predictions for Tesla robotaxis
Elon Musk
Elon Musk's Power Cut_00013520.jpg
Now playing
02:41
Investor: Have to take 'good and bad' with Elon Musk
PHOTO: Tesla
Now playing
01:30
Tesla cuts jobs to offset Model 3 cost
Now playing
03:16
Jim Chanos: Tesla falling behind GM, Audi in software
(CNN) —  

Elon Musk and investor David Einhorn, one of Tesla’s toughest critics, ratcheted up the rhetoric Friday as the two billionaires traded jabs in a long-running battle of words.

The latest round started early Friday, when Musk posted a snarky tweet responding to earlier comments from Einhorn accusing him of fraud. In a shareholder letter last week, Einhorn–who has long bet against Tesla (TSLA) stock–said of the automaker that the “accepted reality appears to be that Elon Musk is above the law.”

In his retort, Musk addressed Einhorn as “Mr. Unicorn,” saying that the hedge fund manager’s letter contained “numerous false allegations,” and offered sympathies for losses Einhorn’s hedge fund have lost money on Tesla. In German, the word for unicorn is einhorn.

“It is understandable that you wish to save face with your investors, given the losses you suffered from Tesla’s successful third quarter,” he wrote, “especially since you’ve had several down years in performance” at Greenlight Capital.

“Please allow us to send you a small gift of short shorts to help you through this difficult time,” Musk wrote, invoking a jab he has used with Tesla short sellers, or investors who bet against a company’s stock performance.

Musk, who is known for publicly sparring with Tesla naysayers, previously sent Einhorn a box containing several pairs of short shorts, to which Einhorn responded with a sarcastic thank you via Twitter.

This time, Musk also invited Einhorn to tour the Tesla factory and learn more about the company, adding “I’m certain your investors would appreciate you getting smart on Tesla.”

Einhorn responded Friday, in an open letter challenging Musk to identify inaccuracies in Greenlight’s shareholder letter and accepting the invitation to visit Tesla factories, writing, “I think facility visits would be fun (can we start in Buffalo?). I might learn the difference between your alien dreadnought factory and cars made by hand in a tent.”

Tesla’s solar panel manufacturing plant is located in Buffalo, New York.

The tension between the two goes back years. Einhorn’s Greenlight Capital has long had a large short position in Tesla, meaning it loses money when Tesla’s stock performs well. Last month, Tesla posted a surprise profit, sending its share price up 30%, and Greenlight took a significant hit.

Einhorn’s letter states that despite losses on Tesla, his firm has returns of 24% year to date. (The S&P 500 index is up 22%.) Even so, the hedge fund has shed more than half its value in recent years, largely due to bets the firm made against big tech companies, including Amazon (AMZN) and Netflix (NFLX).

For years, Einhorn has decried Musk’s controversial leadership style and called for him to be ousted from the CEO seat at Tesla.

His October 30 letter to shareholders rails against Musk’s handling of the SolarCity takeover, which Tesla acquired for $2.6 billion in 2016. SolarCity, which was run by Musk’s cousin, has been the target numerous lawsuits and fraud allegations stretching back to before the acquisition.

One lawsuit filed by Tesla shareholders alleges Musk engineered the purchase of SolarCity, in which he was the majority shareholder, as a a bailout of the troubled solar panel company. That case is heading for trial in March.

Tesla has said the lawsuit is “based on the claims of plaintiff’s lawyers looking for a payday” and that “they are not representative of our shareholders who support our mission and ultimately voted in favor of the acquisition.”

Over the past two years, Tesla’s electric car business has been beleaguered with manufacturing problems related to its rollout of the new Model 3 sedan. The company’s latest earnings report signals the firm may be at a turning point. It posted a $342 million profit, indicating it’s making bigger margins on car sales.

In Einhorn’s letter to Musk Friday, he said Greenlight has “dozens of questions” about Tesla’s finances and questions why the carmaker is “owed over $1 billion by its customers.”

Tesla did not immediately reply to a request for additional comment Friday afternoon.