I'm serious when I say this, and I make no apologies for it, I would do the exact same thing if this were my kid. He's obviously not in any danger. The car isn't moving. He's restrained by the seat belt. He's not vomiting or passing out or harming himself.
He's being extremely funny, though.
There's a scale for how funny drunk/stoned people are, and it is indirectly proportional to the person's age. The younger they are, the funnier it is...y'know, as long as it's all legal, like it is here. I'm not advocating that you get your kid drunk or stoned, film it, then put it up on YouTube. That's just stupid.
Listening to: Huey Lewis & the News - The Power of Love [From Back to the Future]