In the (first) episode of the fairy tale's same name from Happily Ever After: Fairy Tales for Every Child, he is portrayed as an African young boy, and he is the one who points out that "fum" and "African" do not rhyme. He is voiced by Wayne Collins.
In the tale, he is a very poor man (or boy) who lives with his widowed mother. With only a cow, he goes to the city hoping to get some money by selling it, but he is tricked into trading it with some supposed magical beans. His mother gets angry at him, throws the beans out the window and sends him to bed without supper. During night, while Jack was sleeping, the beans sprout a beanstalk who grows into gigantic proportions. Driven by curiosity, Jack climbs the beanstalk and finds himself in the Giant's Realm, where there is a huge castle. There, he sees the owner of the castle, the Giant, who is a woodcutter. Jack notices the two possessions of the Giant, a magical harp who sings by himself, and a goose who puts golden eggs, which the Giant uses to make golden coins.
As the Giant goes to sleep, Jack steals a bag of golden coins and flees. Although the coins were very valuable, he soon ran out of money, and driven by his hunger and greed he once again climbs the beanstalk, this time with a objective in mind. Again in the castle, he waits for the Giant to sleep and steals his goose. Finally, despite knowing better, and due to desire for more adventure, Jack climbs the beanstalk a third time and steals the harp. However, the magical harp alerts the giant, who gives chase after him. Jack climbs down the beanstalk and once on the ground he uses an axe (which his mother has given to him) to cut the beanstalk, which makes the Giant drop to death.
Finally, promising his mother never to do anything like that again, Jack learns that need and greed are two different things, and that without knowing the difference between those two, what one chases ends up chasing him or her instead.
A Somewhat Unorthodox Explanation
Since many will question Jack's inclusion on this wiki as a villain we shall try to explain his crimes in a rather humorous way, though this is a factual account: Jack basically climbed the beanstalk, broke into the giant's home, stole his stuff, and then brutally murdered him; if he were to be tried by modern law, he'd be considered a dangerous criminal, and the giant would be considered a victim.
Jack's Crimes: Theft, Trespass, Assault With A Deadly Weapon (wielding an axe) and Murder.
However, in some versions of the story Jack is the hero as the the giant would plunder his village, and Jack is just returning what has been stolen.