Models walk the runway wearing Yummie Tummie at a fashion show in New York in 2010.

Most reality-TV housewives stick to hair-pulling. But Heather Thomson of the Real Housewives of New York City delivered a legal smackdown to shapewear company Spanx, claiming in a suit filed last week in U.S. district court in New York that its slimming tank tops are copies of designs she patented and sells under her Yummie Tummie brand.

The suit filed by Times Three Clothier LLC, the company Thomson founded to sell her shapewear, asks for sales injunctions against the garments and unspecified damages, including punitive damages.

In January, Times Three sent a cease-and-desist letter to Spanx over the tank tops. Privately held Spanx, whose founder Sara Blakely was dubbed “the world’s youngest self-made female billionaire” by Forbes last year, responded last month by filing documents in federal court in Atlanta requesting a judicial declaration that Spanx was not infringing on Yummie Tummie designs and asking Thomson’s company to pay its legal fees.

“Anyone can make a claim, but it doesn’t mean it has merit,” Spanx said then in a statement that referred to “countless imitators” of its products. “Spanx has not infringed on any valid patent, and we will continue to make fabulous products for our loyal fans."

In the suit filed Tuesday, Times Three said, “Defendant Spanx by Sara Blakely intends to continue its willful and intentional infringement of Yummie Tummie’s design patents asserted herein.” Spanx did not respond to a request for comment.

Thomson told TODAY last month she was “in shock and appalled” by Spanx’s response, although this isn’t the first time she’s taken other garment producers in court. In 2011, Thomson got a $6.75 million settlement in a patent-infringement suit filed against underwear giant Maidenform. That year, it also sued the American subsidiary of manufacturer Li & Fung Group for patent infringement, which Women’s Wear Daily reported was settled for an undisclosed amount.

“I hope she’s ready for war,” Thomson told Women’s Wear Daily last month in reference to Blakely.

So far, it’s shaping up to be quite the battle of the bulge.

For Tiffany & Co., that classic robin-egg blue box and its solitaire sparkling diamond ring signal something quite specific, and the jeweler wants to make sure it stays that way.

When the Fifth Avenue luxury goods powerhouse filed a Valentine’s Day trademark lawsuit against Costco Wholesale, it probably didn’t expect the bulk-buy discounter to counter with its own charges.

Costco says the Tiffany-style solitaire ring – a diamond mounted onto a single band with six prongs, has become so mainstream that it has lost its trademark protection. 

If Costco prevails, the Tiffany name could go the way of aspirin, the escalator, the trampoline and kerosene, which all lost their trademarks as their names fell into generic use, said Gene Quinn, a patent attorney and founder of the IP Watchdog website. 

Read the Tiffany lawsuit (.pdf) and the Costco countersuit (.pdf)

At issue is how Costco was describing some of its diamond rings, according to the Feb. 14 lawsuit filed in the U.S. District Court, Southern District of New York. A customer notified Tiffany that a Costco in Huntington Beach, Calif. was selling discounted Tiffany rings.

A sign in the warehouse-style store stated: “605880 – PLATINUM TIFFANY VS2.1 1.00CT ROUND BRILLIANT SOLITAIRE RING 6399.99,” according to the lawsuit filed by Tiffany.

Costco, in its March 8 counterclaim, says it never told shoppers the ring or its diamond were made by Tiffany, but that the sign refers to the setting. “The style of this ring setting is commonly known as a Tiffany setting. The word Tiffany is a generic term for ring settings comprising multiple slender prongs extending upward from a base to hold a single gemstone,” Costco said.

Tiffany says it’s not buying that excuse.

“Costco’s answer seeks to muddy the waters, but one thing remains clear. The TIFFANY mark is a federally-registered incontestable trademark, has been continuously used for over 175 years and enjoys worldwide fame and recognition as designating superior goods from Tiffany & Co., and particularly Tiffany & Co. diamond engagement jewelry,” the New York-based company said in a statement emailed to NBCNews.

“When Costco used that trademark to refer to goods that had nothing whatsoever to do with Tiffany & Co., they infringed Tiffany’s trademark, while damaging both their own customers and the Tiffany brand. Costco’s counter-claim is an unfounded and weak attempt to defend its willful and infringing use of the TIFFANY trademark. We look forward to proving this in the upcoming court case.”

Contacted for this story, a Costco official said the company does not comment on litigations.

Non-members of Costco may be surprised the warehouse club offers such high-end goods. The Tiffany lawsuit points out that Costco sells legitimate high-end jewelry including Cartier, Chanel and Movado and Breitling. A check of the Costco website even reveals a 3-carat solitaire diamond ring for $99,000 (valued at $154,000.) It does not mention that the mounting is Tiffany-style.

Although jewelers say it is common to refer to a setting as a “Tiffany style,” Quinn, the patent attorney, says Costco is likely to have an expensive, uphill battle defending its use of “Tiffany” instead of “Tiffany-style.”

Given the high stakes, Tiffany will likely fight hard against Costco, Quinn said.

Otherwise, Tiffany risks becoming tiffany. 

UPDATED, 12:48 p.m. EDT: There’s a battle shaping up in women’s undergarments. And lest you think that’s a punch line, at stake in this patent dispute is a billion-dollar industry aimed at fighting the muffin top.

Spanx, a company that’s so successful it made founder Sara Blakely the youngest self-made female billionaire in the world, filed suit March 5 against "Real Housewife of New York" Heather Thomson and her Yummie Tummie brand slimmers. The suit comes in response to a cease-and-desist letter from Thomson's attorneys on Jan. 18. The letter claims Spanx ripped off Thomson's patented three-panel design for slimming camisoles, according to the lawsuit against Times Three Clothier, LLC, which operates Yummie Tummie.

"They have copied my original idea which really was a game-changer for shapewear," Thomson told TODAY Wednesday.

In its lawsuit filed in Atlanta federal court, Spanx argues its tanks and camisoles have unspecified “significant differences” from Yummie Tummie’s design.

Since 2008 Yummie has been producing its patented three-panel Original Tank, made of cotton top and bottom panels with a slimming middle section. The Spanx items mentioned in the suit are the Top This Tank, the Top This Cami and a third, the QVC Total Taming Tank, which is no longer on sale.

Spanx issued a statement about the lawsuit on Wednesday, but declined to say when the items that are the focus of the suit first went on sale.

"Spanx designed our original shaping camisole in 2005 long before Yummie Tummie in 2008,” the statement reads. “Spanx has had countless imitators through the years. Anyone can make a claim, but it doesn’t mean it has merit. Spanx has not infringed on any valid patent, and we will continue to make fabulous products for our loyal fans."

Thomson told WWD that she first learned of the product this past November when she received an anonymous package containing the Spanx Total Taming Tank and a note saying it was on sale at QVC. "I immediately recognized it as my original Yummie Tummie tank,” Thomson told WWD. The unsigned note said Spanx was selling it at QVC. A spokeswoman for Thomson declined to comment further.

"I am still in shock and appalled at this whole situation," Thomson told TODAY.

A personal letter dated March 14 from Thomson to Blakely, posted to the Yummie website, said, “We brought this to your attention expecting you to stop. Instead you’ve chosen to sue us, no doubt thinking your massive company could intimidate ours. We have successfully enforced our design patents in the past and will continue to do so.”

“Sara, I truly expected more of you as a fellow entrepreneur,” the letter concludes.

Officials from Spanx were not immediately available to comment on the letter.