Dad is tall, hairy, and somewhat muscular, with a bit of a gut. He wears glasses and has blonde hair. He is usually seen in a white polo shirt, a striped tie, and brown dress pants. As a baby, he still has blond hair and wears glasses, but wears a striped shirt, wears a diaper and is a troublemaker.
When "Dexter's Laboratory" production was converted from Hanna-Barbera to Cartoon Network Studios, Dexter's Dad's appearance changed the most drastically out of any other character. In Season 3 and 4, Mr. Dad's head is big on the top, but shrinks into a small body, rendering his head in the shape of an isosceles triangle, depending on the direction he's facing.
Loves bowling, golf, fishing, and has an unnatural affinity for his wife's muffins, of which she can expertly create (according to him, the muffins are the reason he married Mom, though this may have been a spur-of-the-moment remark, since he desperately wanted the muffins at the time). Dee Dee's traits inherited from Dad include his cluelessness, naivete, high agility in sports, and blonde hair, though Dexter has inherited his need for glasses and obsession over petty things from him as well. In order to impress Dexter's classmates during "Bring Your Dad to School" day, he pretended that his career was that of an Evel Knievel-esque motorcycle stuntman, mentioning in passing that they wouldn't be too impressed if they found out he was a "boring old scientist." Like his wife, his real name has not been revealed and he is referred to as "dear," "honey," etc. As a baby, he was always a spoiled and rotten child, causing mischief and troublesome. Dee Dee definitely inherited his clueless curiosity- in The Muffin King, Dad runs around the kitchen pushing buttons and creating a mess while mom tries to make her muffins spurring her to yell at him very much like Dexter does to Dee Dee. Also in Sports A Poppin' Dexter mistakes Dad for Dee Dee as Dad yelled 'HI DEXTER' out of the blue exactly like Dee Dee does.
As shown in several episodes, such as "Better off Wet," Dexter's dad can be a bully, embarrassing and pulling childish pranks on his family for his own enjoyment. These often include pushing his family in the pool, and very manipulative behavior. He shows little attention towards the words that exit Dexter's mouth, such as in "Dexter's Lab," where he completely disregards Dexter's statement of taking care of a dog being too much responsibility by assuming that Dexter wants the dog, all the while completely ignoring Dexter's open lab located directly behind him.
His workplace may also be in an office as when Dee Dee takes pictures of him dressed as mom and she says "Wait till the boys at the office see these" in "The Muffin King."
The only thing close to being named was in the episode "Bad Cable Manners" where everyone refers to him as "Mr. Dexter's Dad."
Once tried to get his son into sports, but by episode's end it didn't work. He was once seen smoking a pipe in one episode. While his intelligence is far below that of Dexter's he sometimes gives good advice such as advising Dexter to get his glasses fixed after they were regarded as "cool." Dexter's father normally tends to show favoritism to Dee Dee for her athletic prowess, but will occasionally side with Dexter when facing a challenge between the sexes (such as the snowball war between Dee Dee and Dexter, which he treats as a life-and-death matter in which Dexter must avenge his father being hit with a snowball thrown by Dexter's mother back in college). Dad is also depicted as unreasonably hostile towards everybody when they interfere with a sports-related activity such as watching the "biggest golf match of the year" or breaking his bowling trophy.
- "So, what are we going to have for dinner dear?" - Hunger Strikes
- "Hello Honey, Hello Dexter, Hello Dee Dee, Hello Honey, ... Hello Honey" - Maternal Combat
- "Iv'e got the remote." - Old Man Dexter
- "Dexter, how long have you been keeping this lab a secret from me?" - Dexter's Lab-A-Story
- "Hold out your hands and close your eyes, and when you open them you'll get a big surprise." - Game Over
- "Well, I'd love to stay and chat but iv'e got this sweet love track for your mother." - Game Over
- "How many times have I told you? Early morning is daddy's special bathroom privacy time. MWAHAHAHAHAHAHAHAHAHAHA!!!" - Filet of Soul
- "The boy's right dear I think we need to leave this guy alone." - Streaky Clean
- "Honey, I can't reach the remote." - D2
- "That's what I wanna know mister." - Father Knows Least
- "Nonsense Honey, of course it'll fit" - Ego Trip
- "Ahhh, there you see that dear? The old man's still got it." - Ego Trip
- "Honey, this trophy is the greatest trophy cheap in my tile life. Wait until the kids see this." - The Old Switcharooms
- "You know. I don't want the glue to melt. I'll better cool things down." - The Old Switcharooms
- "A secret? All right, Mr. Bird, you got some explaining to do? Out with it right now!" - The Parrot Trap
- Neither his first or last names were revealed during the series' run and the show's staff simply dubbed him "Dexter's Dad".
- While it wasn't revealed, it was rumored that his real name is "Rob", named after Rob Renzetti.
- Out of all the characters in the show, Dad's newer design changes for seasons 3 and 4 were the most drastic of them all.
- He has a rivalry with Windbear the same way Dexter does with Mandark.
- In the episode "Folly Calls", it was revealed that he was bald and that his hair was really a wig.
- His stupidity may have been passed down to Dee Dee.