CNN Business  — 

Elon Musk — once again — has everyone on Twitter talking.

But this time, the talk is about Twitter (TWTR) itself. On Monday, the company disclosed that Musk has purchased 9.2% of its shares, making him Twitter (TWTR)’s largest individual shareholder. And on Tuesday, Twitter (TWTR) announced that it is appointing Musk to its board. The Tesla and SpaceX CEO also confirmed he plans to push for changes at the company.

“Looking forward to working with [Twitter CEO] Parag [Agrawal] & Twitter board to make significant improvements to Twitter in coming months!” Musk tweeted Tuesday morning.

It’s just the latest chapter in Musk’s, shall we say, colorful, nearly 13-year history on Twitter (TWTR), where he’s played the roles of critic and power-user.

His tweets — which range from commentary about his companies, Tesla (TSLA) and SpaceX, to sometimes controversial statements about pop culture and current events to niche memes — are watched by more than 80 million followers, more than any other CEO on the platform. His (often vague) comments about cryptocurrency have shown the potential to create massive upheaval in crypto markets. And just last month, more than 2 million people responded to a poll he tweeted asking, “Free speech is essential to a functioning democracy. Do you believe Twitter rigorously adheres to this principle?” Around 70% voted no.

Musk’s Twitter presence began facing increased scrutiny in 2018. Over the course of a few months, he joked about tweeting while on Ambien, lashed out at journalists covering Tesla, posted an April Fool’s Day joke about Tesla going bankrupt, and made an unfounded and disparaging claim about a rescuer who aided in the mission that saved a youth soccer team from a flooded cave in Thailand. That led a top analyst to write an open letter encouraging Musk to take a break from the platform.

Musk being Musk, he did no such thing; instead, his behavior on the platform continued to escalate. A month after the open letter was posted, Musk tweeted that he was “considering taking Tesla private at $420” and that he had “funding secured,” sparking a frenzy and sending shares in the automaker up to $371 from $342. The Securities and Exchange Commission later said the funding had, in fact, not been secured and sued Musk for making “false and misleading” statements to investors. As part of his settlement with the agency, Musk must have certain tweets about Tesla reviewed by lawyers before he can post them, a provision he is currently fighting.

Beyond his spat with the SEC, Musk has faced blowback for using Twitter to spread misleading and inflammatory claims about Covid-19, and for mocking President Joe Biden, and Senators Elizabeth Warren, Ron Wyden and Bernie Sanders. Musk also earlier this year tweeted (then deleted) a meme comparing Canadian Prime Minister Justin Trudeau to Adolf Hitler. And he had a widely reported disagreement with a college freshman who rejected a $5,000 offer from Musk to remove a Twitter account tracking the billionaire’s private jet. (Musk has also used his Twitter feed to push back on coverage of himself and his companies that he disagrees with, including taking shots at CNN and other outlets.)

Some other memorable Musk tweets: The time he told Kanye West “you have my full support!” in running for President of the United States. The time he said he was “thinking of starting new university: Texas Institute of Technology & Science” — note the potential acronym there — and said it “will have epic merch.” And then there are the many attempts at marijuana and sex jokes, including this recent example: “Due to inflation 420 has gone up by 69.”

Now, Musk could go from one of the most prominent voices on Twitter to one of the most influential inside the company.

It’s not clear exactly what changes Musk plan to agitate for at Twitter. In addition to his comments about the need to preserve “free speech” on the platform, he has suggested that Twitter should make its algorithm open source. On Monday night, he polled his followers, asking if they “want an edit button,” a longtime feature request, if a divisive one, from many Twitter users.

“While we are not sure about Musk’s intentions — whether he will further increase his stake, become an active shareholder, and/or demand a seat on the firm’s board -— we believe his communication to the firm, other shareholders, and the platform’s 217 million daily active users could affect Twitter’s long-term strategy,” Morningstar analyst Ali Mogharabi said in a note to investors Monday. “Musk could seek to influence the openness of the platform and how it controls content or push to invest in the subscription model more aggressively as it has with Twitter Blue.”

Agrawal, Twitter’s new CEO, tweeted Tuesday that Musk is “both a passionate believer and intense critic of the service which is exactly what we need on @Twitter, and in the boardroom, to make us stronger in the long-term.”

Still, it’s unclear what Musk’s relationship with Agrawal is like. In December, Musk tweeted a meme that equated Agrawal to former Soviet leader Joseph Stalin and depicted Twitter founder and recently departed CEO Jack Dorsey as a former Stalin confidant the dictator later had assassinated. But on Monday, Agrawal appeared to play along with Musk on Twitter, responding to his poll about the edit button by saying, “The consequences of this poll will be important. Please vote carefully.”

Musk has generally appeared to have a positive relationship with Dorsey, who remains on Twitter’s board. The two tech founders have found common ground in their support for cryptocurrency, and Musk expressed support for Dorsey in 2020 when he was facing criticism from some shareholders.

“Just want [to] say that I support @Jack as Twitter CEO. He has a good ❤️,” Musk said — where else? — on Twitter.