From today's NY Times :
How George Clooney and Julia Roberts Quietly Became the Tracy-Hepburn of Our Time
They both praise and roast each other, in interviews and at public events, a tradition that goes back to even before the release of their first film: At a dinner honoring her in March 2001, Clooney called Roberts “a confidante — someone you could call up day or night, and she’d have her assistant call me back.”