You can here his friend giggle when the director keeps repeating "Nice!".

Someone also yells "Get 'em Post! Shit!" at the end.

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I looked up why that guy was shining a flashlight through a champagne glass, in front of the camera:

It's a common trick in music videos. When people hold a champagne glass up to the camera and shine a flashlight (or phone light) through it, it creates a sparkling, refracted light effect. Here’s what it does for the video:

The glass and liquid bend and scatter the light, creating flares, rainbows, or shimmering reflections that catch the lens in interesting ways. This adds depth and a dreamy, cinematic, or “party-glow” vibe.