One day after Mark Zuckerberg's 40th birthday, Elon Musk is back on their old beef, bringing up that fight he challenged Zuckerberg to last year.

"If only Zuckerberg were as tough (sigh). I've offered to fight him any place, any time, any rules, but all I hear is crickets," Musk said in an X post on Wednesday.

Musk was responding to a satirical news story about a hypothetical face-off between President Joe Biden and former President Donald Trump when he mentioned his own proposed battle with Zuckerberg.