In an interview, Derek Flood tells about how he contributed his knowledge of special effects to Shrek 2. The entire interview can be found here.

Bell: What was your special visual effects contribution for Shrek 2?
Flood: I worked in the surfacing department. In CG surfacing involves painting the outsides of objects and characters as well as determining their material properties so wood looks like wood, and skin looks like skin, and so on, instead of it all looking like painted plastic.
One of the main things I did for Shrek 2 was the surfacing for the entire forest sequence where Shrek and Donkey are ambushed by Puss-n-Boots. It was a ground breakingly detailed environment for CG - I had to make surfaces for every conceivable thing you would find in a forest for about a 3 mile radius - from moss covered boulders and giant redwood trees down to oak leaves, acorns, pebbles, and moss. It took months to do, but I was rather pleased with the end results.

Bell: Any memorable moments?
Flood: I also did the surfacing for a lot of secondary characters in the film. In the scene where the King comes into the haunted bar for instance I did almost all of the characters in there - the cyclops doorman, the arm wrestling trees, captain hook playing the piano, the martini sipping frog who hits on the King, and the Ugly Step Sister voiced by Larry King who I think was probably the first transvestite to appear in a cartoon. So I guess Larry King in drag was kind of memorable.

Source: American Chronical