I love this clip. It cracks me up every time.
It was the clip they played on a radio show before their “hate email” segment, but that isn’t important to the clip being fall off your chair funny.
To make it they took a group of musicians and just for the hell of it made them switch instruments and play this song. I love the tentative start to every note and then great gusto and volume at the end when they think they have it right, or at least close enough to being right. There is a joy at being able to make mistakes and to try new things and just generally have a giggle at their own expense.
I know my singing is on par with this band, but I have a long ways to go before my expression of it will be so joyful.