Not much is known about him, except that despite his small appearance, he is quite intimidating. He is easily angered and sometimes even resorts to acting a bit violent such as kicking Robot in Biker Girls. Just as his name implies, his tone is often very loud, which is demonstrated through random outbursts in certain situations. It is mentioned that he may have a family in Monster's Great Escape when he demanded Monster to hurry with with his escape artist act because he was paying for a sitter.
Compared to Perry (and sometimes Robot on rare occasions), he has the worst temper out of any character on the show, and others often either ignore or cope with it.
He is much smaller than his co-workers, even Robot. His metallic exterior is slightly dark red and he sports a thick, slightly crooked antenna with a curved, circular end atop his head. Unlike the other Mechanicals, he has no arms and short, thin, segmented legs. His design, especially his facial features, slightly resembles that of Spitfire's.
- In Security Risk, he was drafted as a baby in one scene. However, this is a one-time gag due to various characters being used in more than one role than their personalities support.
- The fact that he doesn't possess arms is mentioned in First Impressions.
- How he is able to peform tasks that require arms is demonstrated by the use of his mouth as shown in Anger Management when he used it to climb up a stack of crates.
- On rare occasions, he actually shows fear, despite his mostly serious and infuriated demeanor, such as in Grandma's Day Out.
- He has the same voice as Yosemite Sam from The Looney Tunes Show.
- In some episodes, there is a character that looks the same as Loudmouth, only in a blue color. He mainly appears in audience scenes.
- He is similar to Manly Dan from Gravity Falls, due to that they both red and angry, and that they both appear as either background characters or recurring characters that randomly show up in the show, but rarely, if ever, has anything to do with the plot.