Bunnymund is a cool, calm Australian as dry as the Outback. A natural ranger, he is in the dirt, rough and tumble protector of nature. He follows nature's rhythms and when it's time to spring into action he waits for the perfect moment to act. When he finally does, it's all over in a heart beat with the help of his exploding eggs and enchanted boomerangs. Bunny is completely unflappable. The only things that does get under his skin are North's constant ribbing about how Christmas is more important than Easter and his grudge on Jack Frost for causing a blizzard on Easter in '68. (And how Jack use to call him a Kangaroo.)[1]
Bunnymund takes great pride in Easter, and its corresponding season, Spring, stating Spring and Easter represent new beginnings, new life, and the Hope that comes of it. Aside from his tough side, Bunnymund is afraid of Greyhounds.
Bunnymund greatly dislikes Jack Frost due to an incident known as the Blizzard of '68. Beyond it occurring on Easter Sunday, this blizzard and why it caused Bunnymund to hate Jack is unknown, but at the time of the movie, many years later, Bunnymund still held a grudge over it. As a result, Bunnymund was the most vocally against Jack joining the Guardians, even saying that he preferred the Groundhog (who Bunnymund had been hoping wouldn't be the new Guardian moments before) over Jack. He spent a great deal of time arguing with and competing with Jack, but as he got to know him better, seemed to grow to like and trust the young winter spirit. Notably, after Jack helps him with painting his eggs for Easter and have fun with Sophie Bennett, the two are able to share a friendly moment where they joke about one of their previous arguments. However, when Jack appears to have betrayed them to Pitch, all of Bunnymund's trust in him is shattered and he nearly hits the boy, but restrains himself at the last moment. His actions result in Jack getting thrown out of the Guardians and he is surprised when Jack returns to help in the end. He instantly assumes that Jack told Jamie Bennett to make fun of him and is deeply touched when Jamie reveals that Jack made him believe in Bunnymund instead. Indeed, Jack had used his powers to restore Jamie's fading belief in Bunnymund when Jamie had asked Bunnymund for a sign and got nothing in return. During the battle, Bunnymund seems to have regained full trust in Jack again as he fights side by side with him with no issues and even tries to save him from Pitch's attack. Afterwards, when Jack is offered the chance to become a Guardian once again, Bunnymund voices no objections and in fact congratulates Jack on his achievement afterwards saying "that's my boy!"
While Bunnymund doesn't have much experience with children up close, he develops a special bond with Sophie Bennett who is shown to be very fond of the Easter Bunny, always going "bunny, hop, hop, hop." Bunnymund at first panics upon seeing Sophie in his Warren, but once under the influence of Jack's magic snowflake, he has great fun with her, having her help paint his eggs and carrying her on his back around the Warren. When she falls asleep he even holds her in his lap. When the Guardians say goodbye to the kids, Bunnymund admits he is going to miss Sophie greatly and gives her some eggs he painted for her.