NICK JONAS spent Friday night crashing house parties . . . bringing people booze, doing shots with them, and even singing a few songs. Nick is an investor in an alcohol delivery app called Saucey, and on Friday, he played delivery boy to several people in the L.A. area who used it. He rode along on about 10 deliveries over a four-hour period. One woman said, quote, "We were running out of vodka anyways but I never thought he'd show up with my delivery, let alone perform in my living room! It was crazy! He poured everyone shots and took photos. He was super nice." Another partygoer said, quote, "He showed up and sang two songs, 'Jealous' and 'Chains'. And we each had a glass of wine and cheered and all that. After the songs, we chatted for a bit. He was so nice. It was insane!"

(Check out pictures and video here.)