Eleven limousines lined up outside Blair House on Pennsylvania Avenue. And inside, 200 guests came to thank oil billionaire and arts philanthropist Armand Hammer and his wife, Frances, for being the guardian angels of the upcoming 13th annual Meridian House Ball.

It was a premium Washington guest list sprinkled with Cabinet members and ambassadors, socialites and senators, fading tans and the last vestiges of summer's pastel and floral cocktail dresses.

Guests roamed the regal rooms chomping cucumber sandwiches and the everpresent crudite's in curry dip. Quite predictable.

But as Washington parties go, there were a few suprises.

Surprise No.1: The mustache.

"Bob, you've grown a mustache," gasped the hostess, Chief of Protocol Leonore Annenberg, to public relations man Robert Gray. Indeed he had.

"Gosh," mused Gray, "thanks for noticing."

Surprise No. 2: The guest.

"Nellie! John! They told me you weren't coming," gasped Lee Annenberg again. The Connallys recently bought an apartment in Shoreham West and will be dividing their time between here and Houston on "business."

In fact, Nellie and John Connally's appearance there surprised quite a few people. And it was "good to see" every last one of them, drawled Connally. Except a Dallas reporter who has been staking out the former governor and presidential candidate for months.

"Excuse me, sir, but I've been calling your secretary for a while trying to get an interview," said the reporter.

"Well, I just haven't been around much, son," grinned Connally, looking away. End of conversation.

Surprise No.3: The Jelly Belly Man.

"Is that really him," whispered one guest, ogling the man responsible for President Reagan's favorite brand of jellybeans. "I just have to ask him something." She did.

"What ever happened to jalapeno-flavored jellybeans?" demanded the women. "You haven't stopped making them, have you? I can't find them anywhere."

"Oh, no," replied Herman Rowland, like a man who knows his jellybeans. "Write me a note, and I'll get you some."

"I want a big batch," she added, pocketing his card.

As for the Jelly Belly man, he wasn't about to divulge any of the president's jellybean preferences. Well, maybe one. "I heard he prefers the white coconut ones," admitted Rowland with much prodding. "And he hasn't admitted that to anyone. People have just picked it up through observation. He always picks them out." So much for the surprises.

Among the other guests were defense secretary Caspar Weinberger, Attorney General William French Smith, Sen. Strom Thurmond (R-S.C.) and Luther Hodges, president of the National Bank of Washington. "I guess I'm the token Democrat here tonight," Hodges said, looking around.

Also honored were some of the ambassadors who will sponsor private dinners at embassies prior to the ball.

Hammer, who's chairman of Occidental Petroleum Corp., made a personal $20,000 donation for next month's ball which enables the Meridian House -- a nonprofit international cultural exchange organization -- to clear more than $65,000. The ball sold out -- 400 tickets at a cool $175 each -- before the invitations were even printed.

Even Armand Hammer is going this year. "Sure thing," said the 82-year-old Hammer with a wink. "This is sure exciting. And it's an honor to be here tonight. Say, someone said there were some good shrimp around here. Do you know where they are?"