(CNN) -- There are two certainties in airline seat pockets: pretzel crumbs and SkyMall.
And while most travelers try to avoid the mysterious debris left by passengers past, SkyMall has been a welcome addition to the seatback catchalls since the 1990s.
"I found that it was one of those things that anyone who had traveled in the United States kind of knew about," said Mike Barish, a freelance travel writer who reviews SkyMall products for the travel site Gadling. "Some people are in business class; some people are in economy ... some people like to travel, and some people hate it. But everybody knows SkyMall."
The catalog's merchandising team receives hundreds of inquiries every week from vendors, manufacturers and retailers who want their items to be featured, said Joey O'Donnell, customer experience manager for SkyMall.
"We're looking for really special items," O'Donnell said. "We have to look at it and say, 'this solves a problem, and this is so unique. I know our customers will love it.' "
The merchandising team has been doing its job so well for so long that it can just look at an item and know it's going to be a winner with SkyMall's audience, O'Donnell said.
"We have this garden zombie -- the size of a person -- crawling out of the ground," he said. "When I saw it, I was like, 'no way.' But sure enough, it became one of our top sellers."
Other "unique" items aren't so lucky. If you thought the catalog's products were humorous, the list of rejects is downright silly.
"You almost expect them to be fake products from 'Saturday Night Live,' " Barish said. "I think the fact that these things actually exist just makes people happy."
Barish's first experience with a SkyMall product was the SkyRest, a giant, wedge-shaped travel pillow that he reviewed for Gadling in 2008.
"If you brought up SkyMall in conversation, it was the one product that someone would make a joke about," he said. "A) because it was so large and B) because the person in the photograph sleeping on it looked so uncomfortable."
"Seeing these fun, silly things takes your mind off what is normally a very tedious or uncomfortable situation," Barish said of flying.
The same goes for comedian Dan Nainan, who took 84 flights in 2010 and purchases from SkyMall regularly.
"There's that time between when you can't use your laptop when you're taking off and landing, so that's prime SkyMall time," Nainan said. "Their selection is so varied that pretty much anybody from any walk of life could pick it up and find something."
"That was a little bit beyond my budget," he said, laughing. "Once in a while, they'll throw in something ridiculously expensive and frivolous like that."
For Barish, that item was the Cruzin Cooler, which combines "the ability to have cold food or a beverage handy along with the means to get somewhere, without walking," according to its website. For $500, the motorized cooler just wasn't worth it to him. "I don't even know where I'd drive it," Barish said.
The fun nature of the items featured in the catalog reflects the company's attitude, said Christine Aguilera, CEO of SkyMall.
"We're a company that has high expectations for ourselves, but fun is in our corporate motto," Aguilera said. "That's what makes SkyMall what it is. We scour the Earth to find unique and innovative products."
As proved by the popularity of the corpse zombie, it's hard to know what will work until it's put in front of 1.6 million people per day, she said.
But SkyMall wasn't always so quirky.
When it began in 1990, founder Bob Worsley pictured SkyMall carrying mainstream products but quickly found that people were wary of buying everyday items at an airport.
"I think people feel that anything at the airport is going to be overpriced," Worsley said. "So what works are unique items that people can't find anywhere else. If they can buy it at the store, then they will probably buy it there."
Since Worsley's original plans for the catalog evolved, SkyMall is more successful than ever. The catalog is available on 88 percent of domestic flights and reaches more than 650 million air travelers each year, according to its website.
"At the end of the day, while everyone laughs at the silly products, I have to imagine that the thing that keeps them going are the practical items," Barish said. "Not everyone wants to spend money on a conversation piece."
"Products that solve problems are the ones that work best in SkyMall," O'Donnell said. "But strange sells. The items have to solve a purpose, even if that purpose is just making someone smile."
And with the spreading availability of Wi-Fi on flights, Sky Mall has more smiles to look forward to on the horizon. Its deal with GoGo Inflight Internet allows passengers to browse SkyMall for free, escalating what is already a niche market.
"SkyMall is perfect for things you don't necessarily need but would make great conversation pieces if you were willing to be silly and whimsical enough to actually buy them," Barish said. "It solves the problems we didn't know we had until it told us about them."