A slice of pizza? No. But a dozen cheese puffs — or even two dozen if you’re really starving — are fine.

Hamburger? No, no, no. But mini meatballs are okay.

Hot dogs? No can do, buddy. But little pigs in a blanket, served on a platter with honey mustard, are allowed.

In Washington, it’s not the calories that count, it’s whether the food and drink comply with strict ethical guidelines. Even a humble slice of pizza — when proffered by a lobbyist or influence peddler — is classified as a “meal” and, therefore, on the naughty list.

December is a minefield for members of Congress or the administration and federal employees who walk into a reception and have to ask themselves, “Is that chicken wrap compliant with 5 C.F.R. Sec. 2635 Part 203?” That would be one of the many guidelines that govern what gifts can be accepted — including what’s okay to eat and drink at a social gathering.

Tomato Cheddar Soup Shooters, would they count? (James M. Thresher/FOR THE WASHINGTON POST)

We’re wading in shark-filled waters, party-wise. It’s a sincere, complicated and — let’s just say it — sometimes ridiculous attempt to prevent bribes and other extravagant expressions of holiday spirit from corrupting the very core of American democracy. So tricky that a lot of politicians skip the festivities and instruct their staffers not to attend.

“Plenty don’t go to avoid the headache,” one congressional staffer confided. Even those members and lobbyists brimming with Christmas cheer wouldn’t talk on the record because . . . well, who wants to get in trouble for one chocolate peppermint martini?

The gift rule

Every December, the feds send out reminders to government workers about what gifts they are allowed to accept from whom. They are, as you might guess, a scintillating read. But skim at your own risk, for therein lies the difference between enjoying the holidays and getting a call from a congressional ethics committee, which always puts a damper on the new year.

To wit: “This subpart contains standards that prohibit an employee from soliciting or accepting any gift from a prohibited source or given because of the employee’s official position unless the item is excluded from the definition of a gift or falls within one of the exceptions set forth in this subpart.” Gifts include “any gratuity, favor, discount, entertainment, hospitality, loan, forbearance, or other item having monetary value” as well as services, training, transportation, local travel, lodgings and meals “whether provided in-kind, by purchase of a ticket, payment in advance, or reimbursement after the expense has been incurred.” They do not include “modest items of food and refreshments”— soft drinks, coffee and doughnuts — but do prohibit, for the most part, meals. Which is why pizza, the staple of dorm life, is forbidden.

Basically, it boils down to common sense: Expensive gifts from lobbyists aren’t okay. (Definition of Washington old-timer: You remember when three-martini steak lunches were allowed.) A small — under $10 — gift is usually fine, as long as it’s not a regular thing and not from someone who wants something from you.

There are all sorts of exceptions and provisions: The “personal friendship” exception (a present from your college roommate is fine, unless it’s worth more than $250; then you have to get written approval from the Ethics Committee), the “personal hospitality” exception (a fancy dinner or party at a private home, as long as it’s not hosted by a registered lobbyist) and many, many, many more.

The rules for administration and federal employees are slightly different than those for Congress, but they all exist to prevent what we’ll call accidental corruption. Deliberate corruption, such as ex-representative William Jefferson’s $100 bills in the freezer, isn’t the point here. And, to be fair, most federal employees and party hosts work hard to stick to the guidelines and prevent even the appearance of impropriety.

The problem: Figuring out what the heck is okay and what is not.

The reception exception

Which brings us to the basic holiday bash: Most fall under what’s called the “reception exception.” Anyone, even a lobbyist, can host a cocktail party if they’re very, very careful about what’s on the menu.

Meals — or anything traditionally considered meallike — are not allowed. Hence the ban on pizza, burgers and hot dogs. Ditto for pasta stations and chefs slicing juicy roast beef. No fancy wines or designer martini bars. And it’s not okay to go to a fancy party and just not touch the food. Doesn’t matter what you eat, it’s what’s being offered that matters, explained a congressional ethics committee staffer who was not authorized to speak on the record.

Appetizers and passed hors d’oeuvres are fine, unless you try to pass off Beluga caviar as something of “nominal value.” Soda, cheap wine and beer pass the ethics test. And that whole thing about no chairs and the “toothpick test”? A myth. Forks are allowed — for those that like to nibble daintily on cheese cubes — and people are permitted to sit down.

This all fits neatly into the corporate austerity movement, which keeps the One Percent from looking like insensitive fat cats. The trend in cocktail entertaining is Go Small.

“Blowouts are out. Right now, mini is in,” said Bill Homan, co-owner of Design Cuisine catering. “Everything we’re doing is small: What fits on a spoon or one item on a little tiny plate. You have to be creative. We’re doing an item called spaghetti and meatballs: It’s a passed hors d’oeuvre — a pick with swirled pasta on top of a tiny meatball.” Another hit: A demitasse of tomato soup with itty-bitty grilled cheese sandwiches.

Here’s the silliest part of all this: No “meals” allowed, but guests can scarf down as many of the ethically compliant appetizers as they want. Twenty, 30 meatballs, if they feel like it, or a dozen of those addictive mini Peking duck wraps with hoisin sauce — not that we’d ever do that. They are no ethics rules about the amount you can eat, just what you’re eating.

Jumping through hoops

And what about a friendly dinner? Administration officials or members of Congress are allowed to attend any event, even one hosted by a corporation . . . if they write a check for the fair market value. And some do just that. But ethics rules are such that it’s rare for companies to host events in the District and rarer for politicians to attend — which hurts the people of Washington, said event planner Carolyn Peachey: “Corporations in most cities are city fathers and help communities thrive. Everybody forgets there is a city here.”

Politicians are allowed to attend benefits free as the guests of the charity, but everyone has to jump through hoops. “Typically, we send letters to the House and Senate ethics committees four months in advance from charities explaining the event and that it’s widely attended,” said event planner Susan O’Neill, who puts together several nonprofit parties with bipartisan support, notably the American Ireland Fund and Children’s Inn dinners. Officials from the Obama administration typically ask the ethics office to call for information on the party (cost of the tickets, who’s on the guest list) before they accept an invitation. Even then, many are too busy to show up.

Oh, and a “widely attended” party doesn’t mean a big crowd; it means people from all walks of life (businessmen, politicians, diplomats, etc.) instead of, say, just lobbyists.

“The reason for all this is very sound,” O’Neill said. “But the reality is that a member can hold a fundraiser every night of the week and a lobbyist can attend it. We not only need good rules, but good judgment.”

One way to avoid it all?

“I held an open house at my house,” said Rep. Loretta Sanchez, who said she hadn’t gone to a single holiday party — except her own for friends, donors and other politicians. “That way, I know I don’t get in trouble.”