"Fuzzle Trouble" was an episode that appeared in Season 1 of the Smurfs cartoon show.
Gargamel is at work creating his "ultimate Smurf catcher" -- a footprint-finding formula that can reveal the footprints of whoever or whatever the formula picks up. He tests it out using a bellows to spray the formula on the floor of his castle, and it finds the footprints of Azrael, eventually causing him to spring up to the roof with his tail smoldering. Seeing that the formula works, Gargamel decides to make a few adjustments to it, since he doesn't want his Smurfs to be "overdone".
Meanwhile, in the forest, the Smurfs are busy chopping up wood and gathering it in to bring into the village when Clumsy drags along a small round furry creature at the end of a log. Brainy stops Clumsy when he sees the creature at the end of the log, and as Clumsy knocks Brainy over with the log, he sees the creature for himself and finds out just how friendly he is. The other Smurfs gather around, fascinated by this creature Clumsy had found and wanting to hold him. Brainy says Papa Smurf should be the one who sees it first, but as he holds the creature in his hand, he gives Brainy a friendly lick on the face. However, as Clumsy presents the creature to Papa Smurf, he instantly recognizes it for what it is, a fuzzle, and tells the young Smurf to put it back. Clumsy tries to defend keeping him by saying he's so little, but all Papa Smurf could say is "little fuzzles are big trouble." Clumsy then leaves the fuzzle on top of a small mushroom and pats him goodbye before he follows his fellow Smurfs back home with the load of logs they have collected, but as he glances back, he sees the fuzzle sobbing, not wanting to be left alone in the forest. Soon Clumsy races behind the Smurfs carrying the logs with the fuzzle hidden underneath his Smurf hat, telling his smuggled pet to keep quiet or else it will never work.
Gargamel is now testing out his footprint-finding formula in the forest, spraying it on the ground until he finds little red footprints that look like it was made by a Smurf. He now follows the trail of exposed footprints to a tree where he feels a nut fall on top of his head. The wizard shakes the branch of the tree vigorously, telling the "little blue tree toad" to come down from there, when a big angry bear drops right on top of him, scaring both him and Azrael and causing them to duck into the tree for safety. The bear tries to reach for them and to shake them out before he moves on. Gargamel and Azrael peek out when the coast is clear, and notices more Smurf tracks that are heading away from the tree.
Papa Smurf now directs the Smurfs to bring the logs to the dam to make repairs on it. As they do, Clumsy sneaks the fuzzle into his house and gives him a bowl of smurfberries to eat before he departs to join his fellow Smurfs at work. After Clumsy leaves, the fuzzle eats the bowl itself and then multiplies into two fuzzles, then they eat some more objects in Clumsy's house and multiply into more fuzzles.
After a hard day of working at the dam, Papa Smurf rings the triangle and calls for a lunch break. The other Smurfs head back to the village, and Clumsy heads to his house where he finds his fuzzle has disappeared into a cabinet. Thinking he's playing hide-and-seek, Clumsy plays along and says, "ready or not, here I come", as he opens up the cabinet, only to have dozens of fuzzles pop up and cover him. Clumsy quickly rushes to Brainy as he is busy enjoying his lunch, telling his friend he's got a problem. Brainy tries to dismiss Clumsy by saying it's time for lunch and not problems, but then he notices Clumsy's "problem" is now spilling over into his house, eating up things that are in it. Clumsy is now wondering what to do about the problem of the increasingly multiplying fuzzles. Brainy suggests that his friend better do something quickly, as they now see them crawling their way into Papa Smurf's laboratory.
Clumsy enters Papa Smurf's house and hastily offers to bring the village leader more soup as he stirs up the bowl already on the table, until he sees a fuzzle pop out of the bowl. He then grabs a cookie jar and offers Papa Smurf dessert, but soon sees two fuzzles already in there. He next drags Papa Smurf to the door so he could take a walk, but Papa Smurf says he hasn't even eaten yet. As he looks back into the lab, he sees that it has been invaded by fuzzles eating up the things that are in it. He angrily tells Clumsy to round up every last fuzzle and bring them out into the forest right now, which Clumsy immediately goes to do.
Back out in the forest, Gargamel continues to spray his footprint-finding formula while following the trail of footprints it's finding, feeling that he's getting closer to finding them. The wizard finds evidence of trees being freshly cut and chopped down, giving him more of a reason that he's closing on them as he sprays onward.
Back in the village, the fuzzles are now getting everywhere. Smurfette tries to shoo them out of her house with a broom, but a fuzzle ends up eating up her broom and multiplying. Jokey tries to use one of his surprises to scare them away, but the explosion does nothing but create more of them. Clumsy is hard at work collecting all the fuzzles and putting them in a big cart, with Brainy ready to help Clumsy drag them away into the forest after his friend collects what he thinks is the last of them. But as they get ready to pull the cart forward, the pulley breaks off, and they see that the cart is now gone, replaced by even more fuzzles.
Papa Smurf is busy working in his laboratory, sensing peace and quiet, when Hefty enters to warn him that the fuzzles are now at the dam. As the Smurfs are up in arms trying to keep the fuzzles from eating away at the dam, Papa Smurf arrives spraying a formula that puts the critters to sleep. As they soon doze off, he then tells his little Smurfs to quickly and quietly gather up the fuzzles and bring them out into the forest. But as they do, Lazy ends up falling asleep and the fuzzles wake up and return to the dam as he dozes off. Papa Smurf realizes that he has used up all of his sleeping formula and that there isn't time to make up another batch.
Back out in the forest, Gargamel's footprint-finding formula reveals a path of heavy-traffic Smurfs passing through that part of the forest. He surmises that the Smurfs will have to pass by sooner or later, and when they do, he'll be ready for them.
At the village dam, the Smurfs fight a losing battle to keep it from leaking as the fuzzles continue to eat away at it, defeating their efforts. Papa Smurf ends up throwing in the towel, Clumsy is sobbing over the whole thing being his fault, and Harmony gets ready to play a sad farewell tune to "smurfdom as [they] know it". But as the Smurfs groan at the off-key tune Harmony plays, Papa Smurf notices that the fuzzles are attracted to the music, as he sees them swaying to the tune. Papa Smurf then instructs Harmony to play faster, and as he does, the fuzzles come closer to him. The village leader directs him to take the fuzzles out into the forest where they belong, and so Harmony becomes the Pied Piper to the swarm of creatures now following his direction, with the other Smurfs behind them.
Out in the forest, Gargamel prepares a trap for the Smurfs when he hears Harmony's horn playing. He senses that they are coming and so hides himself with Azrael out of sight, waiting for the trap to spring. Harmony passes by where the trap is laid and leaps over the leaves covering the tripwire, but the fuzzles run over it and soon a giant box falls on top of them. Harmony and the other Smurfs duck for safety as Gargamel comes out of hiding with Azrael, gloating over the catch of Smurfs he now has in his possession. As he carries what he thinks are all the Smurfs back to his castle, the other Smurfs decide to head there to find out what's going to happen to the fuzzles Gargamel has captured.
In his castle, as Gargamel opens the box, he finds himself covered with thousands upon thousands of tiny multiplying fuzzles that are spreading around and eating up everything. He curses the Smurfs for this and says he'll get his hands on them for this if that's the last thing he'll ever do. The Smurfs listening in on Gargamel's ranting and raving laugh at his misfortune.