As far as George Alexakis and his three sons were concerned, the only secret at their Pizza Castle restaurant in Falls Church was the recipe for deep-dish pizza.

When FBI agents approached Alexakis and several waitresses last year with photographs of accused spy Ronald W. Pelton, who they said may have used Pizza Castle's pay telephone to communicate with Soviet contacts, they said the man looked familiar -- but not much more so than dozens of patrons who have filled Pizza Castle's black vinyl booths for 10 years.

After a decade of restaurant ownership, said Alexakis' oldest son Kostas, "Nothing surprises you." The disclosure yesterday that Pelton allegedly used the restaurant to arrange "drops" of top-secret materials, he said, "was just like, 'Oh. Another day in the pizzeria.' "

Alexakis' pizzeria, tucked in a string of small shops at 6781 Wilson Blvd. near Seven Corners, draws an eclectic stream of customers -- employes of Climate Heating and Cooling discussing business over coffee, a couple of Bishop O'Connell High School students enjoying sodas and perhaps a few Alexakis relatives who gather in a back booth, talking in Greek and English.

The business, said Kostas, "requires getting used to chaos. It's not the exception, it's the rule . . . there's a strange mixture of people that goes through here."

The Alexakis family moved here 20 years ago from Tarapsa, a small town near Sparta. "My family has been coming to the United States since 1912, in waves. We were the last wave," said Kostas.

George Alexakis bought Pizza Castle in 1976, when it "was . . . nothing," he recalled. "The pizza they served was not good. We worked hard for two years cleaning up the business."

Kostas visited some cousins in Waterbury, Conn., and returned with the idea for deep-dish pies. "I came back with a new pizza recipe, new pizza pans. Business picked up right after that."

The family preserved the restaurant's original decor -- red velveteen wallpaper in a trefoil design, vinyl tablecloths and booths, hanging lamps in ochre glass that give the room a dim, milky look even in broad daylight. Shiny chrome jukeboxes in which "Greek record" is listed along with Cyndi Lauper's "She Bop" hang above each booth.

"We've kept the same tacky wallpaper. I think we kept it because we can't decide if it was put on upside down or not," said Kostas Alexakis.

George Alexakis, his wife Frosso, and his children -- Kostas, 31, Tony, 30, Dimitri, 28, and Joanna, 17 -- work in the restaurant.

"I think we're addicted to the business," said Kostas. "There's nothing to like about it. It's hard work. But I like the personal contact. And your day's never boring."

Kostas paused yesterday, during the lull between lunch and dinner, to eat a steak and cheese submarine sandwich -- "the best in town," he said with a grin.

Henry Rodgerson, sales manager at Climate Heating and Cooling next door, stood at the cash register while George Alexakis rang up his lunch bill.

"Some days we live here. George thinks we live here," said Rodgerson, 39. " . . . Sometimes we hold our corporate meetings here, all the corporate officers. We're here all day, drinking coffee."

At a table near the front, Siobahn Mullen and Susan Clark leaned toward each other across the green gingham cloth. Both are 17 years old, students at Bishop O'Connell High School.

"We just drink. Coke." said Mullen.

"Or ice with lemon in it, because water's good for you," said Clark.

Alexakis and his son said that while they do recognize regular customers, it is hard to keep names and faces straight in the transient neighborhood.

"I have so many that come, so many that know me, but I can't remember the names," said George Alexakis.

The customers -- those aware of the news about Pelton -- have their own concerns about Pizza Castle's new notoriety.

"I hope it doesn't force them to go down on their quality of food," said Rodgerson. "Sometimes, a place is good until it gets a little advertisement."