Jess and Leslie's friendship; he at first is understandably standoffish when she beats him in the first race of the year. Then he's awkward when she thanks him for letting her race with the boys. He comes to respect her spirit and her kindness. She constantly encourages Jess to believe in himself and be proud of who he is. Their bond is so darn beautiful.
Prince Terrien is a Precious Puppy that Jess gifts to Leslie. She's naturally delighted with a huge fluffy boy that follows her. Later, Bill says that he feels like he should have offered Prince Terrien to Jess after his daughter died but can't let go of him. Jess says that Leslie would have wanted her father to take care of the puppy.
After taking part in a revenge prank against Janice Avery, Leslie hears Janice crying in the bathroom. Jess suggests to her that she talk to Janice, and after talking with Janice about her problems, Leslie befriends Janice as a result.
Book
When the kids make fun of Leslie for her parents not having a television, Jess has an Anger Born of Worry reaction: next time, tell him rather than the whole class and she can watch television at his house. Later he stands up to Janice Avery when the latter tries to beat up Leslie for sitting in her seat, quickly getting Leslie to his place on the bus and says that he's not scared of her.
Jess's dad consoling a sobbing Jess as he wonders if Leslie, who died without baptism, is going to hell and encouraging Jess to remember all of the things Leslie taught him.
Jess: Do you believe people go to hell, really go to hell, I mean?
Mr. Aarons: You ain’t worrying about Leslie Burke?
Jess: Well, May Belle said…
Mr. Aarons: May Belle? May Belle ain’t God.
Jess: Yeah, but how do you know what God does?
Mr. Aarons: Lord, boy, don’t be a fool. God ain’t gunna send any little girls to hell.
Just the fact that Jess still cares about Leslie after her death.
The very end, when Jess brings Maybelle to Terabithia.
Jess's thoughts near the end of the book, as he accepts Leslie's death.
For hadn't Leslie, even in Terabithia, tried to push back the walls of his mind and make him see beyond to the shining world—huge and terrible and beautiful and very fragile? (Handle with care—everything—even the predators.)
Now it was time for him to move out. She wasn't there, so he must go for both of them. It was up to him to pay back to the world in beauty and caring what Leslie had loaned him in vision and strength.
Jess’ sisters are much nicer to him following Leslie’s death, but that doesn’t stop Jess from hitting May Belle when she is curious to know what a corpse looks like. Even so, May Belle doesn't hold a grudge: when Jesse goes to Terabithia, May Belle freaks out on seeing him missing and goes to follow him. This leads to her getting stuck on a fallen log across the river. When Jess hears her calling for help, he comes to the rescue and gets her to the banks. He jokingly asks if she was trying to give him a heart attack, only to feel guilty when she reveals she was worried he would die the way Leslie did. Then they have a talk, where Jess admits to May Belle that he was as scared as she was, making her laugh because she can't believe her Cool Big Bro is scared of anything.
Bill and his wife gift Jesse with Leslie's paints, knowing how much their daughter's friend loved to draw. They also don't blame him for what happened, thanking him for being Leslie's friend. When Jess asks if he can also have the lumber behind their house, they say absolutely.
Film
When Jess is racing and seems to be falling behind one of his bullies... and then we see May Belle running alongside, yelling "Go, Jess, go!" and he forges ahead. If not for Leslie, he would have won.
Leslie sincerely thanks Jess for letting her race with the boys. She later offers him gum on the bus. Despite himself, Jess finds himself defrosting and helps rescue her from Janice Avery when Leslie unthinkingly sits in her seat on the bus. This makes Jess realize they are friends.
Jess tells Maybelle that she can't hang out with him and Leslie. Leslie sees how crestfallen Maybelle looks and says that she doesn't play with her Barbies anymore, and would Maybelle like them? Maybelle happily agrees.
Bailee Madison, May Belle's actress, recalls the time she and Josh Hutcherson went through a lot of pep-talk and preparation when they have to argue with each other on set. Every time they film a scene, Hutcherson would break character afterward, asking Madison if she's OK. Hutcherson also had an extreme panic attack when he's supposed to shove his co-star at one point for a climactic scene. While the film does a good job of changing the part where Jesse punches May Belle, Hutcherson still feared that he might torpedo his friendship with Madison and had trouble filming the scene through multiple takes, and repeatedly kept apologizing to her after each one. Thankfully, the push never caused Madison harm on the final take.
Leslie and her parents dance while painting their living room. Jess can't help but smile at the tenderness.
After Leslie's death, Gary, one of the Jerk Jock kids pushes Jess in sight of Janice, the school bully. In the next scene, Gary has a bloody nose, and Janice sits by Jess and is kind to him.
It's especially heartwarming when you remember that Leslie listened to Janice's issues at home, and was very likely the only person who ever did so.
After a trip to church, we get this line from Leslie:
After Leslie dies, Jess punches Scott in the face for making a cruel joke about it. Rather than punish him, Jess' Stern Teacher takes him outside the classroom, gently talks to him, and opens up a bit about how much pain she was in after her husband died. She then tells him a person like Leslie was a rarity, and that she understands that he must be going through Hell — but he isn't alone. Every now and then, the adults say the right thing.
Jess apologizing to May Belle for having reacted badly to her following him to Terabithia earlier, and him noticing that she drew a picture of him freeing the greenhouse pest.
Leslie waiting for Jess after he got kicked off the bus. When he sees she's covered in ketchup courtesy of Janice Avery, Jess lets her clean up at his house.
Jess's dad comforting him in the woods.
Jess: Is it like the Bible says? Is she going to hell?
Jess's dad:(holding him closer) I don't know everything about God but I do know He's not gonna send that little girl to hell.
Jess: Then I'm going to hell because it's all my fault.
Jess's dad: Don't you think that even for a minute.
Jess: But it is. I didn't invite her to go to the museum with me. I didn't wanna invite her. I wasn't there to go with her. It's my fault.
Jess's dad: No, no, no, no. It's not your fault. None of that makes it so. It's a terrible thing. It doesn't make any sense but it's not your fault, Jess.
Contrast to the book, Mrs. Aarons is friendly to Leslie, asking her right away how she's settling in, and chiding Ellie and Brenda, saying they should be glad their brother has a friend.
When Mr. Burke is driving a rental moving van, he has Prince Terrien sitting in his lap, and addresses him by his full name when talking to Jesse. They both seem to be comforting each other about Leslie's death.
