Dooley has shaggy red hair and is always seen with a blank, staring expression on his face. He always sardonically intones something obvious after witnessing an event while making those statements sound like put-downs. For example, after seeing Hank's new lawn infested with fire ants, Dooley says to Hank, "You got ants," and bluntly stating to Bobby, "Your dad got blown up," in "Death of a Propane Salesman". Besides being a put-down artist, Dooley also seems to be something of a bully, taking quiet pleasure in saying things to people to sadden or anger them. For example, when Bill is having fun at Bobby's birthday party, Dooley says, "Your wife divorced you." Another example is when he threw donuts at the kids in the plus-sized fashion show with little or no remorse.
Dooley lives in a two-parent household and has a younger sibling, as shown in the episode where he runs away, although only for a brief period.
Dooley spends most of his time socializing with Clark Peters, another child bully. His voice and manner of speaking are similar to that of Butt-Head from Mike Judge's previous show, Beavis and Butt-Head, albeit without Butt-Head's trademark obnoxious chuckling. Beavis and Butt-Head also had a character named Stewart.
Dooley's trademark is that he usually speaks in phrases of two to seven words. Because of his sardonic delivery, his phrases are generally memorable even when he's talking about something mundane.
- "Your dad's white trash."
- "Joseph likes to watch." (After coming out of Bobby's closet with another girl).
- "Your dad lost his job." (To a random boy during a baseball game.)
- "I'm a suspect."
- "This party is boring. Everybody hates you." (To Bobby at his birthday party after Bobby said a not-very-funny joke.)
- "Tell me more about jail."
- "I want to go home."
- "We're gonna get to see her boobs." (In reference to Peggy's teaching Sex Ed.)
- "There's dust coming out of your butt." (In reference to Bobby's rodeo clown act.)
- "Your lunch money had a Canadian quarter."
- "I peed in some kid's locker."
- "I saw her panties." (On seeing Luanne at a dance being tossed into the air by her partner.)
- "Tú eres puerco." (Spanish for "You are a pig." He said it to Peggy on a Spanish-class field trip when she admonished him to speak in Spanish. Ironically, Dooley speaks better Spanish than she does.)
- "Tú eres muerto (You are dead)." (To Randy after being told on.)
- "I'll die with these horns."
- "I'm gone." (Said in one episode when he ran away, only to return later in the same episode when he announced, "I'm back.")
- "That took courage."
- "You shot her in the eye." (To Bobby, who dressed up as Cupid at a Valentine's Day party and shot a plunger arrow at Connie.)
- "I pass." (In reference to a math question asked by Coach Kleehammer.)
- "I pulled your pants down." (To Peggy, when he acted up in a Spanish class where she was substitute-teaching; she then spanked him in class, which got her in trouble. Earlier in the same episode, he was making fun of Peggy behind her back, and when she told him to stop, he responded, "En Español, por favor (In Spanish, please).")
- "That's the bell."
- "Your wife divorced you." (To Bill)
- "I thought you were fired." (To Peggy when she entered the classroom, saw him, and asked if he was still suspended.)
- "Your feet are big." (To Peggy, when she saw a crude picture of herself with her pants down.)
- "Cool." (After Peggy taught the class about the Spanish Inquisition.)
- "Your grandmother loves you." (After Bobby's secret Valentine turns out to be Peggy's mother.)
- "My future starts today." (In reference to job shadowing for Career Day in "Business Is Picking Up".)
- "My Hank died." (After losing in the Pro-Pain! online game in "Grand Theft Arlen".)
- "Your dad got blown up." (Informing Bobby of the Mega Lo Mart explosion, which Hank was involved in.)
- "Because they're volunteers." (Responding to a student's question as to why Hank, Dale, Boomhauer and Bill can't open the fire hydrant. A Fire Fighting We Will Go)
- "He's a volunteer." (After Bobby confirms that Hank is a fireman.)