David Letterman marks his 20th anniversary at CBS tonight. To mark the occasion, The irrepressible Bill Murray is his special guest. His entrance, in a White Rolls and costumed as Liberace in a flowing white cape and holding a white poodle, drew cheers from the studio audience.

“I didn’t know you had a dog,” Letterman said when Murray joined him at the desk.

“I had to get something to go with this outfit,” Murray replied.

“My heart has taken flight,” Letterman replied, chuckling.

Murray was a guest on Letterman’s first late-night show on NBC in 1982. He was also Dave’s first guest on “Late Show” on Aug. 30, 1993.

Regis Philbin, Tony Randall, Julia Roberts, George Clooney and Brian Williams have made the most appearances on “Late Show.”

In Dave’s 20 years with CBS, nearly 3900 episodes have been telecast, with the show winning nine Emmy Awards. Letterman was also honored at the Kennedy Center ceremonies last year.