Jack Black of Tenacious D performing at Reading Festival 2008 - Day 3. Berkshire, England - 24.08.08

The Tropic Thunder star admitted he has watched celebrity telethons as a cynic in the past - and he wanted to make sure this TV special would be a big winner.

He said, "You know that if one of those lucky so-and-so's donated two per cent of what they made, we could all go back to (TV show) Project Runway."

He then tackled actor Josh Brolin, who was in the middle of a pledge call and ordered him to put the phone down, yelling, "Hang up the freaking phone!"

Black then told Brolin to call comedienne Ellen DeGeneres, who was seated a few desks away from the movie star on the Kodak Theatre stage, adding, "Make a pledge. What did you make on the Coen Brothers (film - No Country For Old Men)?"

Black then turned to the cameras and assured the viewers watching the show, "I'm gonna make these gravy trainers pony up."

Source: WENN