The Humorizer's purpose was to extract Toons' humor so it could be renewed. Once the humor had run through the rinse cycle, it was restored to the Toons to make them funnier than before. Gloomy the Clown and his sidekick Giggles the Frog snuck into the professor's house and swiped the Humorizer from the fridge.
With the Humorizer in his possession, Gloomy started using it as a De-Humorizer. He zapped every Toon he came across, stealing their senses of humor. Toons that were affected started crying uncontrollably. Among Gloomy's victims was none other than Goofy. Gloomy abused the device to the point where it overloaded after the clown zapped the professor.