He must adjust to the life with older, but not necessarily wiser, high school teenagers – including his brother Marcus (Jason Weaver) and Marcus's best friend Mo (Omar Gooding). J.'s missteps of trying to fit in as a kid genius, while being a small kid in high school, as well as the contrast between his smarts and his brother's underachieving nature. Their father Floyd Henderson (John Marshall Jones), a widowed single father who owns his own roofing business, deals with the problems of raising his three kids: Yvette, Marcus and T. So much so, that he becomes the mascot for his school basketball team ("Pugnacious Pete, the Powerful Piedmont Penguin"), which leads to occasional bullying. He spends a fair amount of time at school with his older brother, Marcus, and his brother's best friend, Mo Tibbs. spends much of his time around teenagers, he is occasionally seen spending time with kids his own age, which occasionally results in his attempts to try to fit in with them in situations where he feels out of place. Played by Jason Weaver, the character of Marcus Henderson is T.Older brother Marcus Henderson, the suave and underachieving middle child, also deals with teenage problems, such as finding a date and doing homework (though he sometimes tries to get T. Although they have some tense moments, it is obvious that the two brothers – who share a bedroom throughout the series – care for each other deeply. J.'s older brother and the second-oldest child in the Henderson family (behind sister Yvette).

we were like “Wow, The Mowry’s make some beautiful babies.” But the last time we checked, Tahj hadn’t blossomed like his sisters — maybe we just can’t get over the fact that he still looks like a little boy.

Smart Guy is an American sitcom centering on the exploits of child genius T. Henderson (Tahj Mowry), who moves from being an elementary school student in the fourth grade to a high school student in the tenth grade, attending the same school as his two elder siblings Yvette and Marcus. exhibits exceptional intelligence with an IQ of 180, knows several different languages and has a photographic memory.

Created by Danny Kallis, the series ran for three seasons on The WB from April 2, 1997 to May 16, 1999. Henderson (whose full first and middle name were never revealed) is the youngest child in his family, portrayed as 10 to 11 years old in seasons 1 and 2, and 12 in season 3. He skips six grades from fourth to tenth grade due to his intelligence, after his teachers at his previous school discovered that T. was not feeling challenged enough by a fourth grade curriculum.

The series was produced by de Passe Entertainment and Danny Kallis Productions, in association with Walt Disney Television. C., the show centers on the misadventures of boy genius and youngest child T. Henderson (Tahj Mowry), who at the age of 10 moves from elementary school and gets transferred to Piedmont High School, where he ends up becoming a high school sophomore with teenagers as his classmates. J.'s older sister Yvette (Essence Atkins), usually is the level-headed member of the family – similar to Floyd in that respect – and is the typical overachieving student. Outside of the occasional moments of awkwardness that are bound to occur when a child interacts with high schoolers, T. has a peaceable existence in the school, and is eager to be involved in school functions. is later promoted to being the equipment manager for the Piedmont High Penguins basketball team. plays keyboard for Marcus's band Mackadocious in several episodes, after one of the group's other members breaks his finger in an accident (he also briefly served as the band's manager in the season three episode "Achy Breaky Heart").

He is a forward on his school's basketball team and has several love interests throughout the run of the show, none of which are seen for more than one episode. Played by Omar Gooding, the character of Mo Tibbs is Marcus and T. He is typically portrayed in the show as being dimwitted (such as confusing a rasher with a haberdasher) and sometimes gullible, to the point where in the episode "I Was a Teenage Sports Wife", T. makes Mo part of a placebo experiment by giving him sugar-filled pill capsules that T. claims will stimulate synapses in the brain (therefore increasing intelligence), in order to better perform on tests, only for Mo to inform other students about the pills and flooding T. J.'s bed (having done so as part of a plan to help T. sneak out to see a friend at an arcade after being reprimanded – and effectively, grounded – by Floyd over his choice of clothing).

He is also the lead vocalist for the band which he created, Mackadocious, in which his best friend Mo is the bassist and T. Despite this, Floyd seems to genuinely care about Mo and, as seen in "Diary of a Mad Schoolgirl", shares with him a passion for barbecuing.

Mo all but lives at the Henderson's house and hates eating at his own house (having once chipped a tooth while eating oatmeal cooked by his mother, as he notes in the opening scene of "Get a Job").

In the season three episode "That's My Momma", Mo accidentally overhears a conversation between his parents Delroy and Verla Mae that they had adopted him as a baby – this leads him to have a falling out with his parents and Marcus and T. helping him find his birth mother – who is revealed to be a fortune teller in Delaware named Shelia Ecks. She is in the eleventh grade in season one and graduates high school at the end of season three.

A recurring catchphrase of his throughout the series is, "Hello der! Played by Essence Atkins, the character of Tasha Yvette Henderson – who is generally referred to by her middle name – is the older sister of Marcus and T. Yvette is intelligent, is usually level-headed, is a women's rights activist and has a passion for art, including drama, photography and dancing.