Sarah Blain thinks it's a little weird that she's Santa Claus. After all, Santa is traditionally male and lives at the North Pole, while Blain is a mother of two and lives in southern Florida.

But she's the founder and CEO of Sealed by Santa, a company that makes and sends holiday-themed goods, like signed letters from Santa that are postmarked from the North Pole. The company gained notoriety after Blain appeared on Shark Tank last year. Lori Greiner offered her $150,000 for 20 percent equity, but the deal hasn't closed. 

Blain created the business 10 years ago, with just three products, and has since expanded to more than 15 items, including offerings for other holidays like Easter and merchandise for festive entities like the Tooth Fairy.

Running a holiday-themed business can be tricky. For starters, Blain has to keep it hidden from her 7- and 4-year-old daughters, who believe Santa is real. When her eldest started asking questions and finding some of the company's signature reindeer food--edible offerings for Santa's helpers, made from oatmeal and sprinkles--Blain knew that the business was outgrowing her home office.

Blain says another hurdle of running Sealed by Santa is ordering and selling the right amount of product. While that's key for most companies, Blain's merchandise is often dated (think: ornaments with the year printed on them), making it impossible for her to reuse them the following year. What's more, because the company's winter holiday season is so short (Blain says "Santa season" runs between Nov. 1 and Dec. 15), there isn't enough time to place additional orders.

"If you have one bad year, that's your income for the year," Blain says. "Even though people look at it like a holiday-themed business, you have to work all year round to make sure that doesn't happen."

So far, business has been merry. Sealed by Santa's year-over-year revenue increases by 20 percent, says Blain, with a majority of sales coming during Santa Season. "We do a lot throughout the year, but it doesn't even go near what the Santa numbers are," she adds.

Sealed by Santa is just one of many holiday-related companies that have appeared on Shark Tank in the last eight years. Meet the startups who are also building a seasonal business:

1. Tipsy Elves

This San Diego-based company sells holiday apparel like "ugly Christmas sweaters." Co-founders Evan Mendelsohn and Nicklaus Morton created the company in 2011 after noticing a trend of young people wearing showy sweaters to holiday parties. Two years later, they appeared on Shark Tank and landed a $100,000 deal with Robert Herjavec for 10 percent of the company.

Tipsy Elves has expanded its collection to include other holiday garb like Halloween jumpsuits and Thanksgiving T-shirts. Prices range between $20 and $180, depending on the garment.

2. Geek My Tree

Want to put a spin on your holiday decorations? Geek My Tree sells a variety of lights to spruce up your Christmas tree, including ones shaped like snowflakes and others that change color. The Grand Haven, Michigan-based company appeared on Shark Tank in 2015, and Kevin O'Leary offered $250,000 for 50 percent of the company.

Created by Brad Boylink, the company's products range in price between $9.99 for changeable light packs to $69 for the ornament light show package.

3. Mensch on a Bench

Celebrate Hanukkah with the Mensch on a Bench, a children's plush toy and accompanying storybook. Neal Hoffman, who wrote the story of Moshe, wanted to teach his children about the Jewish holiday while adding new traditions to the family. He created the company--and Moshe, a 12-inch doll dressed in a blue suit and Hebrew prayer shawl--in 2012 and presented it on Shark Tank two years later. Greiner and Herjavec offered him $150,000 for 15 percent of the company.

Now, Mensch on a Bench sells other characters, like the Bubbe (a talking grandma doll), dreidel dog (a blue-and-white spotted pooch), and Hannah the Hanukkah hero. Prices range between $19.99 for the dreidel dog and $249.99 for a 5-foot Moshe.