Glameow was introduced in Pokemon Diamond and Pearl's sequels, Pokemon Platinum, HeartGold and SoulSilver.
However, you can get a Purugly, Glameow's evolution, in Pokemon Diamond and Pearl.
Here's how:
1. Trade: You can trade for a Purugly with someone who has a Pokemon Platinum, HeartGold or SoulSilver game.
2. Find a Shiny Purugly: If you're lucky, you might find a Shiny Purugly in the wild. This is very rare, but it's possible.
Unfortunately, the only way to get a Glameow in Diamond and Pearl is to trade one from a later game.
Let me know if you have any other Pokemon questions! 😊