Ilon Musk had reason to dance this week. His fortune grew by more than $2 billion after Tesla became the most expensive carmaker in the history of the United States. Plus, the billionaire’s girlfriend announced she was pregnant.

At the start of a presentation at the Tesla plant in Shanghai on Tuesday, Elon Musk tore off his jacket and performed a rousing dance to a song by his girlfriend, pop star Grimes. The eccentric CEO and founder of the company had good reason to be in a good mood.

Tesla stock jumped after the company reported last week that it delivered a record 112,000 vehicles for the fourth quarter, slightly exceeding analysts’ consensus forecast, and announced that its first full-service plant outside the United States, located in Shanghai, had begun delivering cars.

In the week to Jan. 9, Tesla stock rose 13 percent, boosting Musk’s fortune by $2.1 billion to $28.8 billion. The 49-year-old billionaire is now ranked 34th on the list of the world’s richest people. About half of his fortune accounts for 22% stake in Tesla. In addition, he has a stake in SpaceX, a private manufacturer of reusable rockets, which is valued at about $12.5 billion.

On Tuesday, the market capitalization of Tesla reached $83 billion. On that day, Ilon Musk’s company became the most expensive automaker in U.S. history (not adjusted for inflation), surpassing Ford, whose market capitalization in 1999 reached $81 billion (data by Dow Jones). By the close of trading on Friday, Tesla’s market capitalization had reached $85.8 billion, not much less than the combined market capitalization of GM and Ford, $87 billion.

Tesla stock has doubled in value since October, but the company has met many obstacles along the way. In November, Musk’s fortune dropped by $768 million in one day after the launch of the Cybertruck electric pickup, when Tesla stock plummeted 6 percent. There is still no consensus among Wall Street analysts on the company. Of the 36 analysts whose opinions were collected by Bloomberg, 15 gave Tesla stock a “sell” rating, 11 gave a “hold” rating and 10 gave a “buy” rating.

Wedbush analyst Daniel Ives is confident in Tesla and points to growth potential in China. “We believe Tesla will be able to increase production and demand in a key region, China, during 2020, which will be a critical driver of share price growth,” Ives wrote in a research note.

It was a busy week for Musk for another reason. His girlfriend Claire Alice Bouchet (the singer Grimes’ real name) posted two photos on Instagram that indicated she was pregnant. Musk has yet to confirm that he is the father. But in response to a tweet with a video of him dancing to Grimes’ song Oblivion, he cheekily replied, “Haha, and you haven’t figured it out yet,” and attached an emoji of the baby. He also left a comment under a tweet with a photo of a pregnant Grimes: “x is y.”