DIDDY DID IT UP FOR ANDRE HARRELL'S 50TH BIRTHDAY PARTY!

Diddy did it up for Andre Harrell's 50th birthday on Saturday night. A source tells us the mogul helped his pal celebrate the milestone at the not-yet-opened Darby restaurant on W. 14th St. with "about 100" other guests, including model Selita Ebanks, Nick Cannon, and DJ Cassidy, a three-course dinner, and a very special surprise: a $6,000, 6-liter personalized bottle of Moet & Chandon Imperial that read "Happy Birthday Andre." Diddy, who hosted the night, gave a lengthy toast to the record executive, while Harrell's friends kept the party going late into the evening.