Classic rockers the Doobie Brothers thrilled fans when they reunited with keyboard player and singer MICHAEL MCDONALD during a TV performance in America on Thursday (20Aug15). MCDonald quit the group in the early 1980s and never rejoined when his bandmates reunited, but he has performed with the Doobies periodically and sat in for a hits medley when the band hit The Tonight Show Starring Jimmy Fallon on Thursday.