X Æ A-12, Elon Musk’s 4-year-old son, ran after his father onto the stage at Mr. Trump’s rally in Washington, DC, and danced excitedly.

Little boy X Æ A-12 made the crowd laugh with delight at President-elect Donald Trump’s pre-inauguration rally in Washington DC on January 19, when Mr. Trump introduced his father on stage as co-leader of the Office of Government Efficiency (DOGE).

“Come up here Elon, did you see the rocket launch yesterday? And 𝑏𝑎𝑏𝑦 X is here too,” Mr. Trump introduced billionaire Elon Musk and X Æ A-12.

The boy jumped and waved as Mr. Musk presented his plan to cut federal spending and streamline government operations.

“Little X followed me on stage,” Mr. Musk, 53, introduced his 4-year-old son. “As you can see, he’s very supportive.”

In his speech, Mr. Musk pledged to cut government spending by up to $2,000 billion, emphasizing DOGE’s mission to “Make America Great Again” and “Make America Strong for Centuries.” He revealed that DOGE is hiring engineers and aims to quickly expand its staff to 100 people.

X Æ A-12 is the son of Mr. Musk and singer Grimes. The boy’s name sounds like “Ex Ash A Twelve” in English. Grimes once explained that X means unknown, the word Æ sounds like the word AI (artificial intelligence), A-12 is the name of a high-altitude reconnaissance aircraft of the Central Intelligence Agency (CIA), the type of aircraft that she and Mr. Musk both love.

Mr. Trump once praised 𝑏𝑎𝑏𝑦 X as “beautiful” and “perfect” during a photo session with family members on election night, January 5. The 𝑏𝑎𝑏𝑦 was held in his father’s arms, taking a photo with Mr. Trump’s family.