Musk posted a cryptic message that suggested he was listening to Elvis or considering a potential tender offer to take control of the company.
The latest in the saga is a tender offer. Musk believes shareholders should decide the company's future, not the board.
In premarket trading, the shares of the company were up more than 3%.
The board collectively owns almost no shares, with Jack leaving, he said on Fridy.
The CEO of the two companies offered to buy the company for $54.20 a share, which would value it at $43 billion. A poison pill is a shareholder rights plan adopted by a company to ward off a hostile takeover.
Musk has a 9% stake in the company. Musk was offered to join the board, but only if he could not buy more than 14.9% of the firm. Musk made a bid to take the social network private.