From Bulbapedia, the community-driven Pokémon encyclopedia.
Nick (Japanese: ニック Nick) is a character of the day in Celebi and Joy!. He is the son of an unnamed carpenter and befriended a young Nurse Joy and Ritchie.
Nick is first mentioned by the elderly Nurse Joy, who revealed that he was one of her childhood friends. It was also revealed that his father helped build the first Pokémon Center in Marion Town. The elder Joy described him as shy and reserved but he still was a kind boy. Tragically, he and his father died in a rock-slide right after they left Marion Town. Joy felt that if he would have come to the opening party of the Pokémon Center instead of leaving then he might have lived.
Unbeknownst to Nurse Joy, Nick had carved her a small statue of Celebi, the shrine's protector. He was going to give it to her as a present but was too shy to give it to her. Instead he hid it in a dresser that was given to the Pokémon Center. Ritchie was the one to discover it and when he did Celebi appeared and transported him and Sparky back in time.
Ritchie soon met Nick in the past, right after meeting the elderly Nurse Joy as a child. Nick was trying to fix up the old Celebi shrine. He acted the same way that the elderly Nurse Joy had described. Ritchie then found out from Nick's father that he had a small crush on the young Joy. Nick claimed that he didn't and started to eat his food fast.
Later that night, Ritchie saw Nick carving the small Celebi statue that he found in the dresser before he was transported. Ritchie tries to convince him to give the statue to Joy and to tell her how he felt. He still wasn't sure though. Soon, a friend of Nick's father came to the house and said that the young Joy was missing. This was not good because a thunderstorm was going on at the same time. A search party was then sent out to find her. However, Nick already figured out where she went.
He realized that Joy probably went to go protect the Celebi shrine from the thunderstorm. Nick and Ritchie soon found Joy lying unconscious near the shrine. The both took Joy into a small cave for shelter. Afterwards a lightning bolt hit a tree and it fell on the shrine and it started to burn. Nick did his best to try to put the flame out so that it wouldn't burn the shrine but to no avail. Ritchie told him to get away from it but he refused saying that the shrine was Joy's favorite thing in the world and he wouldn't let anything happen to it. Soon Joy awoke but another lightning bolt was about to strike Nick. Both Joy and Ritchie ran for him. They all seemed to be doomed until a green light appeared. Celebi had come to protect them and the shrine. Soon after that the storm subsided.
The next day, just like history had told, Nick and his father left Marion Town and on to their next job. Joy was upset that he left. Soon then Ritchie went over to the desk and looked in the secret compartment where he left the Celebi statue. Ritchie then borrowed Joy's Ponyta to find Nick. He stopped in front of him on the mountain path and explained again that he should be there for the party. Nick finally agreed and he and his father headed back towards the city. As they did, the fatal rock slide that would have killed them passed right behind Ritchie.
At the party, Nick finally gave the Celebi statue to Joy. Celebi then visited Ritchie and Sparky and they were sent back to their own time.
When Ritchie returned to the present day, he found out that not only was Nick alive, but he was the mayor of Marion Town. The older Nick felt that he had met Ritchie somewhere before and asked him if he has been to Marion Town before. However, he just told him that he "passed through in the past".