On his way to Lake Acuity, Mew had to cross through or across Mount Coronet. As he was out for adventure, Mew chose to cross through the mountain ridge. It was something about it that made it more fun to scour through dark passages and meeting new pokemon.
Once inside mount Coronet, Mew flew through the maze like tunnels. He saw many kinds of pokemon he hadn't seen before. Like with Mt. Moon, there were a lot of Zubat and Golbat enjoying it inside. Beside those two types, there were also a lot of Machop and Machoke. Mew enjoyed himself a lot when he saw them performing some kind of sumo wrestling competition, Machop against Machop, Machoke against Machoke.
Mew cheered from the side lines and gasped in enjoyment when the winners of the competition evolved. Like that there was one more machoke and one Machamp to lead the group. Having done their competition, the group moved on and so did Mew.
Every now and then Mew also met some Clefairy and their previous forms, Cleffa. As fun as it was, Mew handed out a moon stone every time he met a Clefairy. If they wanted one he gave one, if they didn't, then Mew wouldn't give one.
After that there were a lot of Meditite, Geodude, Bronzor, Chingling and all their evolved forms. There were a lot more different kinds than in Kanto. Everytime Mew discovered a Pokemon he hadn't seen before, Mew would sneak up from behind them and observe what they were doing. Stuff they found interesting, Mew would observe as well. If Mew liked it enough, it would be thrown in the subspace.
Like that, Mew spent a few days to weeks inside Mt. Coronet until he finally left the mountain range, ending up in a snow covered area. Having seen snow for the first time, Mew dove in and out of every heap he saw. When a pokemon passed by, Mew would play around with them by throwing snow balls and sharing food.
The other pokemon were all too happy to play with this little visitor, especially afterwards when Mew left heaps of food or much needed evolution stones.
Spending a lot of time with an Abomasnow and Frosslass family, Mew enjoyed himself to the limit as they played around, making all kinds of figures in the snow. When tired they would return to the cave, but as soon as they woke up, they would continue playing.
After spending another few weeks with the pokemon family, Mew said goodbye again to the little friends he made and went on towards something that looked like a giant moving snake. From the front smoke rose to the sky. Interested in this strange creature even Mew had no knowledge of, Mew followed it and ended up near Lake Acuity. Having lost interest as soon as he arrived near his destination, Mew flew above the lake, waiting for Uxie to come out and play with him.