Throughout the series, Timmy is defined as proud and arrogant. Although clever and witty at times, it's mostly his greed and ignorance that get him into trouble along with his fairies. Despite this, Timmy has been shown to be brave and caring as well, usually when his friends or family are in danger.
He along with his friends are deemed "unpopular" by the student body even though he seems to be of middle-class income. He constantly tries to improve his social status to impress his life-long crush: Trixie Tang.
Being a ten year old boy, Timmy has a very small attention span and hates vegetables.
Timmy has gained weight about four times in the TV series.
The first, and perhaps most well-known, was in the episode "Just Desserts", when he wished that every meal was dessert. He along with his classmates became abnormally overweight.
Another time was in the episode "Truth or Cosmo-quences" when he drank a large pitcher of lemonade, causing his belly to swell from under his shirt.
He briefly became bloated after eating a large amount of his mother's magically enhanced cooking in "Food Fight".
Finally, Timmy also shortly gained weight during the events of "Timmy's Secret Wish" after eating a tub of frosting.