Milestone birthday for "Boy Meets World" star William Daniels ... he's just made it 99 trips around the sun!!! William, who famously played Mr. George Feeny on the hit 1990s sitcom, celebrated his 99th birthday Tuesday in Los Angeles ... marking the occasion by going to Art's Deli with his wife, actress Bonnie Bartlett . William and Bonnie have been married almost 75 years, a major accomplishment especially in Hollywood, and lunch at Art's Deli has become a birthday tradition for old Bill here.