Strange creatures at the National Zoo are nothing new, but the one on display in the education building is a rare breed indeed.

It is uncaged. Loves company. Thrives in air conditioning. It's mostly red, white and brown. Sometimes with a head that's pointed and green. Sometimes a head that's big and yellow. It never bites. It sings and does tricks without coaxing.

It's an actor dressed as a professor dressed as a dinosaur.

Welcome to "Dinosaurs, Dinosaurs . . . A Mesozoic Musical," playing at the National Zoo through Labor Day weekend.

The show, which opened in April, draws 50 to 70 guests to each performance, zoo officials say. Three times daily Tuesday through Friday and four times daily Saturday and Sunday, children and adults descend on the education center to hear and see 260 million years of dinosaur history condensed into 40 minutes.

Along the way, lead character Professor Finemore sings, dances, jokes and dons at least five dinosaur heads.

Tyrannosaurus, of course, is there and green. Brontosaurus (more properly called apatosaurus, you learn in the show) is yellow.

The show is produced by Slim Goodbody Corp. and Dinamation International Corp., the company behind the moving dinosaur exhibit at the Museum of Natural History. They bill it as "a 40-minute, one-man show that blends science, entertainment and audience participation."

But the one man is actually either Eric Burgan, 29, or Kenneth C. Jackson, 30, both professional actors with roots in the Washington area. Each does 10 shows a week. Yes, it's fun, they say. But they also think it will help their careers.

"First, it's a one-man show, which is very good for an actor to get under his belt," said Burgan, relaxing after a show as Jackson prepared for the next.

"You get all the director's attention," Jackson said.

"A lot of people think children's theater is easy to do, not like 'real' theater," Jackson said. "It's not easy to do well. It's pretty . . . easy to do badly."

Doing it badly would lose the audience, they say. Which would make the show as dead as, well, dinosaurs.

So at one point, Professor Finemore divides the audience of children and parents into herbivores (plant eaters) and carnivores (meat eaters).

"If all you eat is meat, meat, meat, what are you?" sings Burgan.

"A carnivore!" scream the meat eaters, adults as loud as children.

"But if you go for fruit and nuts and shoots, what are you?"

"A herbivore!" yell the plant eaters.

That's not all. Carnivores lift one arm and extend the other downward as they reply, then bring both together to symbolize the sharp teeth of a carnivore tearing apart its prey. Herbivores spread their arms wide, then hit their palms together with a clap to symbolize the flat teeth of a herbivore chewing on a shrub.

Yes, grown men and women, along with their children, actually do this on command. Happily.

"The show was wonderful, excellent," said one mother on her way out.

"When the kids are into it, the parents really get into it," said Kate Broderick, the show's stage manager.

"I love to see whole families of herbivores and carnivores," Burgan said.

He means it.

When you play a professor of dinosaurs, Burgan and Jackson have found, you'd better know your stuff. Enough to list all the categories, explain their evolution and expound on their extinction. And the questions -- such as "How do you spell parasaurolophus?" -- are fast and furious.

"Children these days are sophisticated," Burgan said. "They know what they're talking about."

And if they didn't before, they know when they leave that parasaurolophus was a duck-billed dinosaur whose mating call sounded like a trombone: "I'm pining . . . (womp, womp, womp,) to get you in a game of footsie . . . my tender little two-ton tootsie," the professor sings.

The trombone is attached to a football helmet, which Burgan or Jackson wears during the ditty. But that's one of the few parts of the show they don't explain -- or like to talk about, for that matter. The helmet is a New York Giants helmet.

"We have a Redskins one," said Burgan. "It just doesn't fit."