Please visit his article on the South Park Archives for more information.
Randy wears a blue colored shirt with chest pockets on each side and dark gray trousers. Under his jacket, it is implied is a white shirt. His left-side pocket usually has a yellow, a red, and a blue pen with a pocket protector. He has thick, black hair with parted bangs, and a thick black mustache, both of which seem to evoke a 1970s hairstyle. In early episodes, though, his hairstyle was somewhat different (see left). He also has a dimpled chin.
Randy is often portrayed as an intelligent but simultaneously dim-witted, quick to think, naive man, while all the same a caring, doting father. However he is also obsessive and when he gets engrossed in something, his personality turns to the exact opposite. He becomes immature, childish, and dumb during the obsession phases. He has a habit of being led astray by new fads or events, like many of the characters. All the same, he has also been known to go completely against such things, though his reasons are usually selfish and immature. He will also try to do a heroic thing, but will then be distracted due to a selfish reason. Randy also seems to drink a lot of coffee, shown carrying a cup in most episodes he is in at one point or another.
Randy has a tendency to act very melodramatic. Whenever things get surreal, Randy calls for his son, he usually puts on an act of being very ill and weak, and moaning Stan's name out: "Staaaaaan!". Randy is also shown to be a hypochondriac.
Randy Marsh has been a breakout character among casual fans, who find him hilarious, but is extremely controversial among those who produce fanworks, who often feel that he is overshadowing other characters, such as the children. He is, as a result, not a common focus of fan fictions or fan art. As a result, he has gained a significant number of detractors, particularly on websites like Tumblr, though he remains popular on other social media sites like Reddit and Facebook.
Trey Parker has stated an intention to ease back on using Randy in the show as of Season 19, but has admitted he often uses Randy because as he gets older, he feels more like Randy as a character than like the boys.