A source told told Us Magazine, "Rob led the crowd singing for her, and you could tell she was so embarrassed but in a cute way!"
Stewart and her guests chowed down on oysters and hors d'oeuvres as well as a "simple chocolate cake" created by a private catering company. Witnesses say Stewart and Pattinson made no attempt to conceal their affection for one another: "Rob and Kristen were together all night. They held hands and he kissed her cheek a bunch of times."
Stewart was treated to a big birthday surprise: Another source told Us that people pitched in to buy Kristen a motorcycle.
"Rob was so excited for Kristen and they each took turns riding it. Kristen learned to ride a dirt bike in New Moon so they thought it would be appropriate. Rob was supervising as she sat on it to make sure she was ok. They looked like they were having a great time, and it will be something they can really enjoy!"
Maybe Rob and Kristen will use the new bike for an impromptu road trip after their next projects wrap up. Stewart is starring in the upcoming adaptation of Jack Kerouac's On the Road, after all.