Joaquin Phoenix's Clown Prince of Crime is back in theaters this October with "Joker: Folie à Deux" -- and he's got backup this time from Lady Gaga's Harley Quinn.

The celebrate the movie's release, we've pulled together some of the best merch for DC's most troublesome twosome ... who have had their faces slapped on everything from t-shirts and sweaters to neon lights, purses and more.

Order now and show your Joker or Harley pride when the movie opens October 4.

Put on a Happy Face ... or this t-shirt reminding you to do just that.

Featuring Phoenix's made-up mug from the first movie, this shirt puts Arthur Fleck's face front and center. The Unisex Ultra Cotton tee comes in six different colors, including Joker green, purple, black and navy.

"Really good quality and fit perfect," read one 5-start review. "Good conversation starter as well.. ... first time I wore it several people discussed parts of the movie with me at work and in the grocery store."

Celebrate the Joker and Harley's twisted love story with this shirt highlighting them both.

With cartoon versions of the pair in a heart surrounded by the words, "You're the Joker to my Harley Quinn," this tee is also perfect for couples looking to show off their love for each other ... and the DC characters.

"Love this shirt," wrote one happy customer, who added that, "like Harley Quinn and Joker," the top  "fits perfect."

With that fall weather creeping in, show your supervillain support with this Joker and Harley sweatshirt.

This "100% authentic, officially licensed Batman hoodie" is unisex, with the couple's faces above the pocket. Not feeling this dark heather gray version? It also comes in navy blue and royal blue.

The pullover comes with a classic fit and twill-taped neck, which will keep you warm if that movie theater AC is blasting.

Light up your life with this Joker neon light.

Joker fans looking to spice up their interior decorating should grab this LED sigh good for the bedroom, living room or man cave. It's a USB-powered device, that comes with a dimmable switch -- as well as a chain or screws for hanging.

"I love how vibrant the color is! Great addition to my sons room," said one satisfied customer ... while another added, "Nice features and works well. Looks good and having a dimmer is even better."

Want to dress as Arthur Fleck for his return to theaters? You're in luck with this Joker costume.

The polyester suit includes green shirt, orange vest and matching red pants and blazer ... though face paint and green hair coloring or wig will have to be purchased separately to complete the look.

"Really nice. Price was great!!!!! Fast shipping," exclaimed one 5-star review.

There's a ton of fun merch to show your love for Harley Quinn this year, starting with this crossbody bag inspired by her costume.

This premium vegan leather bag measures 8.0 x 6.0 x 2.5 inches, with space enough to hold your phone, wallet, keys and more while you watch the movie in the theater.

Officially licensed by DC comics, the red and black accessory from Buckle Down is a stylish way to support Harley this season.

A more whimsical option is this Harley Quinn Mallet Bag.

Inspired by Harley's weapon of choice, the mallet purse comes in her signature red and black, with the word POW emblazoned on one end. The stylish accessory also also features a zipper closure and wrist strap.

"Love this bag so much!" exclaimed one customer, who pointed out the bag was out of stock at Spirit Halloween. "I was glad to find here. My phone fits perfectly and it could hold more items, which is impressive for a wristlet."

Cuddle up in Harley Quinn with this cardigan sweater inspired by the femme fatale.

One half red, the other black, the button down features a giant playing card with Harley in her traditional harlequin clown getup on the back ... as well as additional, smaller cards down the sleeves. It also has heart-shaped buttons and her diamond design on the front.

"I absolutely adore this sweater. I'm a big Harley Quinn fan, especially this version from the 90's animated series," read one 5-star review. "It fits great, and it looks adorable."

Look just like Lady Gaga's version of the character in this Harley Quinn blazer from Hot Topic.

This new iteration is sure to be one of this year's hottest Halloween costumes and fans can get the jump on the look by grabbing this diamond-pattern jacket with ruffled sleeves now.

Finish off the look with some face paint, leather skirt and diamond tights to look just like Gaga!

Even your pooch -- or hyenas, if you're anything like Harley -- can get in on action with this Harley Quinn dog collar.

The officially licensed collar is made from high-density polyester and steel, with Hot Topic assuring buyers that it's "built to last."

Featuring a seatbelt button design and black and white diamond-inspired artwork, your little Puddin' will be the talk of the dog park.