Jack Dorsey said he's 'really happy' Elon Musk is joining Twitter's board. Take a look at the evolution of their crypto bromance.

The Twitter CEO said Musk's account on the social platform was one of his favorites.

"He's constantly on Twitter, constantly talking about what [Tesla is] doing — and how he's feeling about it as well," Dorsey said at a trade show in 2016. "He's very open and using it to correct press and if people aren't focused on the right things. I think he's a really good model of how to use it well."

Dorsey asked Musk for "direct feedback" in a video call in front of thousands of Twitter employees.

The Tesla CEO said it would be helpful to tell fake and real users apart.

"Is this a real person, or is this a bot net, or a sort of troll army, or something like that?" Musk said.

An activist hedge fund that had amassed about a 5% stake in Twitter pushed an initiative to drive Dorsey out of his role as CEO. The hedge fund, Elliot Management, reasoned that since Dorsey led two companies, Twitter and Square, he wasn't focused enough on the former.

Musk — who also helms two companies — tweeted, "Just want say that I support @Jack as Twitter CEO. He has a good" heart, using the heart emoji.

—Elon Musk (@elonmusk) March 3, 2020

Hackers staged a coordinated attack on dozens of celebrity accounts last summer, and Musk's was one of them. He told The New York Times that he personally called Dorsey after realizing he was hacked.

"Within a few minutes of the post coming up, I immediately got texts from a bunch of people I know, then I immediately called Jack so probably within less than five minutes my account was locked," Musk told the Times.

Dorsey especially has thrown his support behind the digital currency, which has seen booming popularity and growth recently.

The Twitter CEO has simply "#bitcoin" in his account bio and said at Miami's bitcoin bonanza last year that "Bitcoin changes absolutely everything. I don't think there's anything more important in my lifetime to work on."

And he said in a series of tweets in mid-2021 that Square was toying with building out a hardware wallet for bitcoin.

Musk has said he strongly believes in crypto, and Tesla said at one point it would accept vehicle purchases in the form of bitcoin. The CEO also included the #bitcoin hashtag in his Twitter bio at one point.

But last year, Musk announced the company was suspending bitcoin payments over concerns around the use of fossil fuels for bitcoin mining and transactions. He said Tesla would start accepting it when at least half of bitcoin mining is powered by clean energy. 

Musk has kicked off market rallies for the tweets he posts about cryptocurrencies, much to the anger of regulators and investors.

For example, he tweeted in 2021 "my Shiba Inu will be named Floki," a reference to the  Shiba Inu that represents dogecoin. The altcoin shot up 16% just minutes after Musk published his tweet.

Dorsey posted about an upcoming bitcoin event called "The B Word" on Twitter in the summer 2021, and after Musk responded to it, the Twitter CEO invited him to attend for a conversation.

Musk responded, "For the Bitcurious? Very well then, let's do it," and added a wink face emoji. Dorsey said he would set it up.

The virtual chat in July 2021 was the first public appearance starring the two friendly executives. You can watch a recording of it here.

In March, Musk became Twitter's largest shareholder after buying up a 9.2% stake in the social media giant.

Musk is also becoming a Twitter board member, and the company's current CEO tweeted his support early Tuesday for the news, calling Musk a "passionate believer."

Dorsey shortly after tweeted something similar.

"I'm really happy Elon is joining the Twitter board!" Dorsey said. "He cares deeply about our world and Twitter's role in it. Parag and Elon both lead with their hearts, and they will be an incredible team."

—jack⚡️ (@jack) April 5, 2022