He is actually less of a true hero of the original book. However, as far as the adaptations go, Wilbur is still useful even way before he takes Charlotte's egg sack home.
He is voiced by the late Henry Gibson in the 1973 film, David Berón in the 2003 DTV sequel, and Dominic Scott Kay in the 2006 live-action film.
When farmer John Arable decides to "do away with" the runt of a litter of pig, his daughter Fern intervenes, telling him that it is absurd to kill it just because it is smaller than the others. John decides to spares the piglet and let Fern raise it as a pet. Fern nurtures it lovingly, naming it Wilbur. Six weeks later, Wilbur, due to being a spring pig, has matured, and John tells Fern that Wilbur has to be sold (his siblings were already sold). Fern sadly says good-bye as Wilbur is sold down the street to her uncle, Homer Zuckerman. At the farm, a goose coaxes a sullen Wilbur to speak his first words. Although delighted at this new ability, Wilbur still yearns for companionship. He attempts to get the goose to play with him, but she declines on the condition that she has to hatch her goslings. Wilbur also tries asking a rat named Templeton to play with him, but Templeton's only interests are spying, hiding, and eating. Wilbur then wants to play with a lamb, but the lamb's father says sheep do not play with pigs because it is only a matter of time before they are turned into smoked bacon and ham. Horrified at this depressing discovery, Wilbur reduces himself to tears until a mysterious voice tells him to "chin up", and wait until morning to reveal herself to him. The following morning, the voice reveals herself to be an araneus cavaticus named Charlotte living on a web overlooking Wilbur's enclosure. Charlotte tells Wilbur that she will come up with a plan guaranteed to spare his life.
Later, the goose gives birth to seven goslings, one of which, named Jeffrey, befriends Wilbur. Eventually, Charlotte reveals her plan to "pay a trick on Zuckerman", and consoles Wilbur to sleep. The next morning, Zuckerman's farm assistant Lurvy sees the words, SOME PIG, spun within Charlotte's web. The incident attracts publicity among Zuckerman's neighbors who deem the praise to be a miracle. The publicity eventually dies down, and Charlotte requests the barn animals to devise a new word to spin within her cobweb. After several suggestions, the goose suggests the phrase, TERRIFIC! TERRIFIC! TERRIFIC!, though Charlotte decides to shorten it to one TERRIFIC. The incident becomes another media sensation, though Zuckerman still desires to slaughter Wilbur. For the next message, Charlotte then employs Templeton to pull a word from a magazine clipping for inspiration, in which Templeton returns the word, RADIANT, ripped from a soap box to spin within her cobweb. Following this, Zuckerman decides to enter Wilbur into the county fair for the summer. Charlotte reluctantly decides to accompany Wilbur, though Templeton at first has no interest in going until the goose tells him about all the food there. After one night at the fair, Charlotte sends Templeton on another errand to gather another word for her next message, in which Templeton returns with the word, HUMBLE. The next morning, Wilbur awakens to find Charlotte has spun an egg sac containing her unborn offspring, and the following afternoon, the word, HUMBLE, is spun. However, Fern's brother Avery discovers another pig named Uncle has won first place, though the county fair staff decides to hold a celebration in honor of Zuckerman's miraculous pig, and rewards Zuckerman $25 and a gold metal. Zuckerman then announces that he will allow Wilbur to "live to a ripe old age".
Exhausted from laying eggs and writing words, Charlotte tells Wilbur she will remain at the fair to die. Not willing to let her children be abandoned, Wilbur has Templeton retrieve Charlotte's egg sac to take back to the farm just before Charlotte dies. Once he returns to Zuckerman's farm, Wilbur guards Charlotte's egg sac until the winter. The next spring, Charlotte's 514 children are hatched, but leave the farm causing Wilbur to become saddened to the point of wanting to run away. Just as Wilbur is about to do so, the ram points out that three runty spiderlings did not fly away. Pleased at finding new friends, Wilbur names the spiderlings Joy, Nellie, and Aranea. But as much as Wilbur loves them, they will never replace the memory of Charlotte.
The live action version is slightly different than the book and original film. Here, Fern Arable wakes up in the middle of the night (as opposed to daybreak) and sees a light in their barn. Even though it’s raining, she rushes in as she knows its time for the mother pig to give birth. True enough, she finds a dozen piglets and her father, John. John noticed the runt, and saw that since the sow couldn't feed the runt, he felt like he had no choice but to kill the little piglet as he hesitantly picks up the runt and an axe. Fern saves the runt, as she finds it ‘unfair’ that being born small gets no break in life. Fern nurses the pig and even brings it to school (which gets Fern into trouble), and do so many things that show how much she is taken by her pet.
However, the pig is getting bigger. Her father persuades Fern to ‘sell’ Wilbur (the pig) to her Uncle Homer Zuckerman, who lives just across the street. Even though not technically hers anymore, she still lavishes the same affection for her pet, saying “Goodbye” to Wilbur as she goes to school and “Good night” before she goes to bed.
In the barn, Wilbur meets the locals, Ike (the horse), Mr. Gussy and Mrs. Golly (geese), Samuel (the top sheep), Mrs. Bitsy and Betsy (cows) and Templeton (the rat). The locals are kind but are slightly aloof, for they know what happens to ‘spring pigs’ come winter.
Her mother feels slightly concerned for her daughter’s behavior and one night, prevails upon Fern to stay home and do her homework. Wilbur feels abandoned, as this is the first night Fern hasn’t said “Good night” to him. A kind voice tells Wilbur to sleep well as he is not alone, he is with a friend.
Wilbur wakes up and looks for the source of the voice. It was a spider (Charlotte), who Wilbur, in all his innocence, welcomes with open arms. The other animals do not particularly like this new denizen (especially Ike who is afraid of spiders) but accepts her just the same.
Templeton gives Wilbur the cold hard facts, ‘spring pigs’ do not see the snow of winter. They are led up to the ‘smoke house’ where they are served to the family for the holidays. Charlotte, however, promises Wilbur that she will do everything she can to prevent this from happening. They set to thinking.
One night while spinning her web, Charlotte notices that a stray strand from her web resembles the letter ‘S’. She gets an idea and starts to rework her web.
In the morning, the human folks are surprised to read ‘some pig’ in a spider’s web. Word spreads and soon, the whole countryside goes to the Zuckerman farm to see for themselves this small ’miracle’ in their midst. Fern and Wilbur bask in their fame but the townsfolk interest fades as the spider’s web fades.
Charlotte calls out a meeting to suggest the perfect word for Wilbur to make him sound special. Charlotte orders Templeton the rat to go to the dump and bring a magazine clipping with a very special word. Templeton selfishly refuses until the animals point out that if Wilbur is slaughtered, then that would also mean that the pig's trough, which is also Templeton's primary source of food, remains empty, and therefore, the rat would also die. Templeton reluctantly obeys. He brings Charlotte a piece of paper with words. Charlotte decides upon a word that describes Wilbur and sets to work in the night. Templeton goes to his usual ‘dump’ where he narrowly escapes two crazed crows and brings Charlotte a piece of paper with words. Charlotte decides upon a word that describes Wilbur and sets to work in the night.
The next day, the human community is again abuzz as the word ’terrific’ is clearly spelled out in the web. Wilbur and Fern again share in the limelight of this new ‘miracle’. But like the last time, interest faded with the web.
Summer turns to autumn and Charlotte and Wilbur are desperate. The humans have shown no sign of changing Wilbur’s fate come winter. Charlotte then spins the word ‘radiant’ in her web and the community is alive again. Basking in the glory of this latest ‘miracle’, farmer Homer decides to enter Wilbur in the upcoming county fair. Charlotte initially refused to accompany Wilbur, as she is expecting but changes her mind in the end. Templeton goes along for the ‘treats’ to be found in the fair.
At the fair, Wilbur is pitted against Uncle, a huge specimen of the piggy folk. Charlotte turns to Templeton for one last word and he delivers. Charlotte, heavy with babies, spins her web one last time.
In the morning, the Zuckerman family is disappointed that the judges arrived early and awarded the blue ribbon to Uncle. However, the fair is turned upside down as the folks crowd to see Charlotte’s last word for Wilbur – “humble”.
One of the fair’s governors asks the Zuckermans to accompany them to the stage where they pin a Governor’s medal to Wilbur. That and a check finally ensure Wilbur’s life. As Wilbur and the Zuckermans are cheered on, Charlotte lays dying after laying her eggs. Wilbur arrives in time for one more poignant exchange and with Templeton’s help, takes home Charlotte’s eggs to the barn. In the winter, Wilbur is spared as the Zuckermans have a happy holiday.
In the barn, the folks there take turns watching Charlotte’s eggs, even Ike who rises from his fear to take his turn in the ‘hatching’.
Spring comes again and the spiders hatch. As the spiders are carried away in the breeze, Wilbur is sad as he will have no one to share Charlotte’s memory with. Turning back to the barn, Wilbur meets three spiders who decide to stay. They all became friends and life goes on in that ‘extraordinary’ town.