Kendall Jenner may be 18, but a source says she displayed diva behavior at Mercer Kitchen last Monday. Jenner was dining with Stephen Baldwin's daughter, Hailey, and was unhappy when "the staff wouldn't serve her [booze] because she's underage," our spy said. "Kendall got up and left and didn't pay for all the food . . . about $60 worth, and without a tip."

Her server, Blaine Morris ran outside to ask the celebuspawn to pay her bill.

"Kendall and Hailey started laughing," our witness said. "Kendall took a couple of $20 bills out of her wallet, threw them at the server and walked away, not even counting if it was enough or if it included a tip."