He wanted to visit Misty

After some long minutes of welcoming and enjoying each others company Ash asks his old friend for a favour.

"Do you think you could get me to Cerulean city?" Pidgeot didnt even reply, but instead just pushed Ash on his back, lifting him in the air with no problems whatsoever. He flew with an incredible speed. Ash still knew, tho, that it wasnt his fastest, as he had seen in the Pokedex that a Pidgeot could reach up to Mach 2 in flight.

As they reached Cerulean he was dropped off right in front of the PokeCenter. He thanked his friend and got him treated inside quickly, just to make sure he was alright, before he said goodbye again.

"Now, lets not get busy before we meet our friends. Lets head for the gym!" And so he did.
As he reached the gym the gym, tho, what he found was an ongoing fight. A croud had gathered and the ranks were filled with visitors, so he first expected the water show to be on today, but it wasnt. On the one side he saw Misty, and on the other... Wow, those were her sisters, Lilly, Daisy and Violett.

'Didnt they agree on the sisters making the show and Misty leading the gym? What is going on here?' He thought to himself.
"Alright everyone, this fight will decide it once and for all. If the Sensational Sisters win this fight, our little sister has to partake in our Awesome water show. If she on the other hand wins, it will be her call who will partake from now on. Misty has to win with two Pokemon against our six combined. The battle starts now."

Loud cheering from all around Ash bursted out as the Pokemon were selected. It didnt take long for Misty to take the upper hand. Her Pokemon clearly were the better trained ones, as she used them in gym battles often. Her Starmie defeated one Shellder and a Luverin with ease, but then somehow lost to Seaking. Her second pick was Gyarados which defeated Seaking, Goldeen, and Seel. The last round was against the Sisters Dewgong.