Wall Street is happy over Tesla's quarterly results and guidance, but Elon Musk's apologies to analysts may make investors even happier.

On Wednesday's post-earnings conference call, Tesla took its first questions from the two analysts Musk had dismissed three months earlier, when the company reported first-quarter results. That day, the stock plunged in after-hours trading in response to what Musk called "boring, bonehead questions" from analysts.

This time, Musk showed contrition and Tesla shares surged 8.5 percent in after-hours trading Wednesday, adding about $4.75 billion to the stock's value. The stock closed up 16 percent Thursday.

"My apologies for not being polite on the prior call," Musk said, blaming his behavior in part on a lack of sleep and overwork.

"I appreciate that," said Bernstein analyst Toni Sacconaghi, in response. "Thank you."

And Wall Street took notice that perhaps Tesla's chief executive will not distract investors with problematic behavior going forward.

KeyBanc Capital Markets called it "maybe the most valuable apology of all time."