Just last night they played celebrity charades at a benefit for the LAByrinth Theater Company in NYC. "They were on the same team," a source tells us. "They hi-fived when the game started. At one point, everyone was dancing to 'Dancing Queen' and Amanda and Justin started dancing really close. They couldn't take their eyes off each other."
The lovebirds were first linked together in August when US Weekly reported they started "going on date-like activities" after being longtime friends.
Also at the Patron tequila-sponsored fundraiser last night were Padma Lakshmi, Bobby Cannavale and Josh Charles.
Also spotted out and about…
Leonardo DiCaprio playing backgammon and throwing dice as a hot mystery girl looked on over his shoulder at Goal in West Hollywood.
Michael Douglas having dinner with his dad Kirk Douglas and his wife Anne at Boa Steakhouse in Santa Monica.
Former American Idol judge Randy Jackson spending a few hours with some friends at Chi Lin on Sunset Boulevard.
Mary-Kate and Ashley Olsen having Sunday lunch at Casa Vega in L.A.
Jane Lynch digging into some Slavic dishes at Mari Vanna LA.
Josh Groban enjoying calamari at Kona Grill in Kansas City, Missouri.
Ashlee Simpson and boyfriend Evan Ross having dinner with friends at Pace in West Hollywood.
—Additional reporting by Zach Johnson and Baker Machado