According to the National Retail Federation, consumers will spend nearly $5 billion on Halloween-related merchandise this year -- an average of $59.06 per consumer, up from $48.48 a year ago. Yes, Halloween has become a big business, and it's not just for humans anymore. Pet-supply retailers are scaring up big profits with costumes for dogs and cats. According to the American Pet Products Manufacturers Association, more than 3.5 million Americans will buy Halloween pet products this year -- a 40% jump from two years ago. And according to the APPMA, pet owners spend an average of $17 per gift -- which translates to $59.5 million on Halloween pet products.

So if you're planning on dressing up your Chihuahua like Charo this Halloween, you're not alone ... OK, maybe you are. But plenty of other "pet parents" will be playing dress-up, and that's good news for Petsmart (NASDAQ:PETM), the country's largest pet-supply retailer. Michelle Friedman is the brand communications manager at Petsmart. The Motley Fool's Mac Greer recently talked with her about the business of Halloween.

Mac Greer : How big is the Halloween business for Petsmart?

Michelle Friedman: It's becoming more and more popular every year. It's something we've especially seen grow in the last five years. We don't give specific numbers out for these categories, but we can tell you that it's something that's absolutely exploded in the last two years.

Mac Greer : Let's talk about the most popular costumes. What am I looking at if I'm looking for a Halloween costume for my dog?

Michelle Friedman: In terms of popularity this year, we had a new one that was extremely popular. And I say "was" because a lot of them are sold out. And that's the fireman costume -- replete with red hat and yellow raincoat.

Mac Greer : Are we talking boots?

Michelle Friedman: No boots. Just the ensemble of the hat and coat.

Mac Greer : What other options if I'm looking for a Halloween costume for my dog?

Michelle Friedman: We have something called our costume tee, which is a full costume but fits almost like a T-shirt, so it's one piece that slips right over the head. So it has the good mix of form and functionality.

Mac Greer : (laughing) Form and functionality? Do you think that matters to the dog?

Michelle Friedman: (laughing) And to the pet parent as well. We always do recommend safety along with the costume because it's a fairly new category that pet parents don't have a lot of experience in. So we recommend something that doesn't block [the pet's] vision.

Mac Greer : How about a couple of other dog costumes?

Michelle Friedman: The cow, complete with udder. We have a duck costume this year that has webbed feet. And online we have some of the superheroes [and villains!] that tend to be really popular -- Superman, Batman, Darth Vader, and Princess Leia.

Mac Greer : Now earlier you used the phrase "pet parent." When did that phrase come into vogue? It sounds like very shrewd marketing to me.

Michelle Friedman: I don't know when exactly, but it's something we're really sensitive to, because our shoppers aren't just customers -- they are, in fact, parents to their pets. This fits in really well with Halloween, because just as parents would shop for their children for a costume, they do the same thing for Halloween for a pet. So they're taking into account their own fashion sense.

Mac Greer : Now let's talk about cats. If I want to dress my cat up for Halloween, what costume options am I looking at?

Michelle Friedman: Cats, as most people know, are very different personalities from dogs.

Mac Greer : They're a bit skittish.

Michelle Friedman: Yeah, and they can be a little more finicky. So we offer cat hats for cats. We just started offering those last year. We offered three different styles, and this year we've doubled that to six because they've been so popular. These come in everything from a witch to a pumpkin to a pig. And the best seller is the devil.

Mac Greer : The devil. Wow! That may say something about how people feel about cats. . Are you gonna dress your pets up for Halloween?

Michelle Friedman: Ummm, no. I have a 12-year-old Labrador. For the holidays she does the Santa hat because she knows she gets a treat for it.

Mac Greer : But she's not going to be a fireman?

Michelle Friedman: No, she's a senior pet. And Halloween costumes aren't for every pet. And pet parents know the personalities of their pets. They know what they'd be comfortable in. For instance, my co-worker has a miniature dachshund named Roxy who's sporting a hot-dog costume, and she's quite happy in it. So there's no problem there.

Mac Greer : And along those lines -- is it wrong if I dress my dog up as a cat, and my cat up as a dog?

Michelle Friedman: (laughing) Again, I think it depends on the personality of the pet.

Mac Greer : Live and let live.

Michelle Friedman: Yes.

Mac Greer : Michelle, Happy Halloween -- thanks for joining us.

Michelle Friedman: Thanks so much.

Petsmart is a Motley Fool Stock Advisor recommendation.

At the time of publication, Mac Greer held shares of Petsmart. He has no plans to dress his dogs up for Halloween .

The Motley Ghoul's Tricks or Treats represents the opinions of each Fool only and should in no way be taken as the opinion of either The Motley Fool, Inc. or any company in question, or as representative of anyone or anything other than that specific Fool's thoughts. So do your homework, and review The Motley Fool's disclosure policy.