When CIA Director Stanfield Turner and FBI Director William Webster both appear at a calm little opening for a Canadian musical, you almost begin to wonder what's up.

"It's an undercover operation," expalined Webster's wife, Dru.

But no, said webster, who was eating cheese and crackers. He and Turner are just good friends of Canadian Ambassador Peter Towe. They go to football games and Halloween parties together.

An theater openings, like the one last night at Arena Stage for "Billy Bishop Goes to War." It's Canadian, so Towe hosted its American premiere and invited about 100 people to the party afterwards.

As his wife, Carol, put it: "We didn't attract spies. We attracted friends."

Among them was director Mike Nichols, who really behaved like a director. He stood in a corner of the room, sipped champagne, smoked a thin cigar and told reporters he had to catch a plane. To others, he lowered his voice to a whisper, then said he had laryngitis and couldn't talk.

Nichols was around because he plans to be producing the musical when it reaches New York, probably in April. In the meantime, he's eyeing it closely.

Last night, he called actor Eric Peterson and singer John Gray back behind a velvet curtain in mid-party for tidbits and pointers. "The ending is still under discussion," explained Gray, who also wrote the play about a Canadian who joins Britain's Royal Flying Corps.

Gray, as it turned out, was an emotional wreck. "I broke out into a nervous rash," he explained as people dipped strawberries nearby. "Really. An last night I couldn't sleep. I've had insomnia for two months. I much prefer the rash."

As he spoke, a sympathetic friend named Kay Staley slipped him a tube of ointment.

Despite his opening-night anguish, most would say Gray's life has changed markedly for the better since Nichols walked into the Legion Hall in Listowel, Ontario (population about 5,000) a year ago. "Billy Bishop" was playing there. ("We've done this thing at Legion halls and funeral parlors and everywhere," explain Gray.)

Nichols thought it was terrific. So here it is in Washington.

Among the party guests were Sens. Howard Metzenbaum (D-Ohio) and Edward Zorinsky (D-Neb.) and Burke Wilkinson, a novelist who said he actually met Bishop, the World War I flying ace, at an officers' club in London.

"There he was," said Wilkinson. "Very jolly."

Also jolly was Towe, the host. He plans to keep his job, he said, even though the Canadian government has changed once again.

"Everything changes," he offered, saying nonetheless that he expected American-Canadian relations to stay the same. But what of Prime Minister Pierre Trudeau's recent talk of economic nationalism and his hints at loosening ties with Washington?

"Our relationship is a constantly changing relationship," Towe offered again.

From there he went on to matters closer at hand.

"Where do you find the peanuts?"