Because Jirachi is initially considered to be the second most powerful Mythical Pokemon, as it's established that he's second in line to Arceus[1], he abuses his rank and wishing abilities to wreak havoc and cause mayhem. He's pretty carefree, and acts rebellious, as according to him, the Legendaries don't follow the rules, so "why should he?"[2] This implies that he was once an obedient and decent legendary who initially followed the rules, but after witnessing the Legendaries constantly breaking the rules, had his behavior negatively influenced and began his rule-breaking nature. Jirachi acts overly confident in his abilities due to being able to wish his way into getting out of problems. Whenever the mythical mon is angry, he "evens out" his anger by seeking vengeance; however, his methods of enacting out vengeance includes manipulation, such as the time when he created a false story on how he resurrected Tepig to pin the blame on both Cyndaquil and Bulbasaur, while at the same time
