Woozles are an odd race resembling weasels (hence the name similarity) and their main objective is to steal all the honey possible. It is currently unknown if Woozles are bad or good creatures (like Heffalumps) by Pooh and his friends. In The New Adventures of Winnie the Pooh, Woozles are seen and often mentioned by Tigger throughout the series. The only known Woozles to physically appear in any Winnie the Pooh related media are a villainous thief named Stan, and a giant named Wooster. While Stan fulfills the original idea that Woozles are usually evil thieves who have much in common with honey-snatching Heffalumps, Wooster proves they can be turned good, depending on the Woozle's personality and how they are treated by others.
In Winnie the Pooh and the Blustery Day, while Pooh fell fast asleep, he has a nightmare about the Heffalumps and Woozles surrounding him to steal his precious honey. They also had the ability to transform like the Heffalumps do, like a bandleader Woozle transforming its nose into a fife with a horn end, a white Woozle who briefly turns into a square, and a small Heffalump transforming into a tall skinny Woozle.
In My Friends Tigger & Pooh, Darby, Tigger, Pooh, and the others leave out treats for some Woozles, although no Woozles are seen or come. However, at the end of the episode, all the treats are gone and presumably eaten by the Woozles (so they could be nice or gentle creatures). If The New Adventures of Winnie the Pooh and My Friends Tigger & Pooh are both meant to fall within the same continuing storyline within the Winnie the Pooh universe, this could mean that much like humans in real life, some choose to make good decisions (like Wooster), and others choose to make bad decisions (like Stan).
In Christopher Robin, while Woozles do not physically appear, they are mentioned along with Heffalumps several times by the residents of the Hundred Acre Wood, to which Christopher Robin doesn't believe their existence. Woozles are mentioned even more by Pooh and friends when they are trying to return Christopher Robin's paperwork to him with the help of Madeline, where they mistake Giles Winslow Jr.'s last name with "Woozle", and believe that Christopher will be eaten by one if he doesn't have his papers. At the end of the film, Giles gets called a Woozle by Christopher, and Pooh tells Madeline that that is what a Woozle looks like. Christopher describes a Woozle as a monster that gets everybody else to do work for him, to which Giles Winslow Sr. agrees that Giles Winslow Jr. certainly is a Woozle by the sound of one.