Think billionaires just sit around inside their vaults swimming in dollars, Scrooge McDuck-style? That sounds great and all, but Bill Gates and close pal Warren Buffett have an idea of fun that's more like two middle-school pals. In a virtual-reality video Gates tweeted out Wednesday, the two cruise around in a golf cart, eat Dairy Queen treats and croon "I've Been Working on the Railroad" while Buffett plunks his ukulele.

The two go tooling around in the cart at the annual shareholders' meeting for Buffett's company, Berkshire Hathaway. Things get off to a rousing start when Buffett warns the driver, Gates, that he better have Geico insurance (owned by Berkshire Hathaway). They then make a stop at the Dairy Queen booth (also owned by BH), where Buffett selects his favorite vanilla-orange bar, and Gates picks a Dilly Bar. (Gates pays for both, to Buffett's amusement.)

But the highlight of the video comes at 2:59 when the duo pass a train exhibit and Buffett gets the Microsoft co-founder to sing along to "I've Been Working on the Railroad" while he plays his instrument. (Buffett said in 2015 that he tried to learn the ukulele in college to impress a girl, but never learned more than three chords.)

If you have a virtual-reality headset, Gates suggests you watch the video on a mobile phone, but you can also watch it without one.

The Gates-Buffett love affair didn't end with Wednesday's inevitable brain freeze. On Thursday, Gates tweeted out a photo collage of the pair's 25-year friendship, plus a link to an essay praising his pal. Sounds like the Dairy Queen treats weren't an aberration. Gates says the 85-year-old Buffett "has basically stuck to eating what he liked when he was 6 years old."