At the beginning of Toy Story, Woody and Buzz were originally rivals with Woody showing jealousy toward Buzz for apparently being replaced as Andy's favorite toy and Buzz thinking himself to be a real space ranger. Their misunderstanding of each other eventually leads them to being separated from Andy, captured by Sid, and subsequently taken to his house. After Buzz finally finds out that he is a toy, he becomes too depressed to help Woody, but with Woody's words of encouragement, Buzz gradually comes to terms with what he truly is, and the relationship between the two starts to improve. After Woody saves Buzz from Sid's clutches, Buzz thanks Woody as they shake hands, and their friendship is born. The two toys then work together to reunite with Andy, and by the end of the film, they become the best of friends.
In Toy Story 2, after Woody is kidnapped, Buzz vows to rescue his best friend and goes out on a mission to bring him back home. When he finally catches up with Woody, he becomes upset with his friend's decision to stay with his group and leaves him to contemplate his decision, as Woody has become convinced that Andy will eventually give him away. However, when Woody comes to his senses, he calls to Buzz to inform that he is going home with him, to Buzz's relief. After returning home following a successful rescue mission, the two toys agree to be there for each other even after Andy outgrows them.
In Toy Story 3, the two have a falling out when Buzz declares that he and the other toys, believing that a now college-bound Andy does not want them anymore, are going to Sunnyside Daycare after being mistakenly thrown out by Andy's mother, which Woody has witnessed. When Woody declares his intention to leave Sunnyside to go back to Andy, Buzz offers him a handshake, which Woody refuses, upset that his friends have seemingly given up on their owner. After Buzz is reset into Spanish mode, Woody convinces Buzz that the toys are "amigos" to get him to rejoin their side. When Buzz is restored back to normal, Woody, as with the other toys, is joyous that he has returned. After the toys are dumped into the furnace at Tri-County Landfill, Buzz and Woody take hands and glance at each other for what could have been one last time if not for the Squeeze Toy Aliens controlling a giant claw that rescues the toys from the incinerator. Soon after returning home, Buzz and Woody shake hands, unable to admit that the two best friends are separating ways after all they had been through. However, Woody leaves the note for Andy telling him to donate the toys to Bonnie, and after they are handed down to her, Buzz comforts Woody as they accept that their lives with Andy is complete and begin their new lives under Bonnie's care.
Buzz's relationship with Jessie is only hinted at the end of Toy Story 2 when Buzz became instantly lovestruck with her looks and her adventurous personality. Jessie immediately returns his compliments by describing him as the sweetest space toy she has ever met.
In Toy Story 3, their relationship hasn't evolved much since Toy Story 2, but it's shown that Jessie is fond of Buzz, and he is protective of her. After their "Operation: Playtime" plan fails, Buzz gives an exceptionally sad look to Jessie as she climbs out of the box, and also gives her sympathetic looks when she has panic attacks and when they argue about going to Sunnyside. Before getting taken to Sunnyside, Buzz is shown being a little more concerned over Jessie when she goes into a panic attack and says "We're being abandoned!" Even later, in the demo mode which he is put in by Lotso and his minions, he remains attracted to Jessie, calling her a "temptress" with "bewitching good looks". Then again, after being reset into Spanish Mode, Buzz is shown to be even more attracted and open toward her, calling her "my desert flower", dancing around her, asking her to join him in his adventures exploring the galaxy, shielding her from Mr. Potato Head when he sees him as a threat, getting jealous when she hugs Woody, and saving her from not only being pinned under the trash, but from a falling TV set. Jessie first shows signs of strong feelings for Buzz during this rescue, and when he is first thought to have perished after the TV set falls on him, she is clearly in despair. When Buzz returns back to normal, Jessie is overly joyous and relieved that Buzz is alive. However, it is actually during the incinerator scene when they truly realize their feelings for each other. And after the group is rescued, only Buzz and Jessie continue to be holding hands after the claw delivers them all to safety. During the credits of Toy Story 3, the two finally seal their relationship, with Jessie taking the initiative for the two to dance an exciting paso doble that closes the trilogy.
In Small Fry, when Buzz makes it back to Bonnie's room, Jessie is overjoyed to see Buzz, she rushes over to hug him.
When Buzz first revealed himself to the rest of Andy's toys, Rex was relieved that he wasn't a dinosaur and further expressed curiosity over the functionality of Buzz's buttons. Buzz didn't seem to mind and later on, they bonded with each other when Buzz gave Rex some tips on how to be more scary, tips which helped him let out a loud roar at Mr. Potato Head. Rex was horrified when Buzz was accidentally knocked out the window by Woody but loyally stayed awake into the night in an effort to find him (though with no success).
In Toy Story 2 Buzz is shown to help Rex with his video games and gives him tips on how to defeat Zurg. He even encourages him by saying "You're a better Buzz than I am." When Woody is later kidnapped by Al McWhiggin, Rex accompanies Buzz and the others, thinking his video game experience has prepared him for real life combat. When they're in Al's Toy Barn, Rex, like the other toys, mistakes Utility Belt Buzz for the real Buzz but becomes overjoyed when the real Buzz meets up with them again in Al's apartment. Rex would later serve as Buzz's navigator when they hijack the Pizza Planet Truck in pursuit of Al to the airport, successfully getting them to the airport, though he has a little trouble identifying left and right.