Unlike other Pokemon that only speak their name, Meowth is able to speak the English language. He is also able to walk upright. And as presented in the picture above, he sometimes wears clothes.
This is all because of what happened when he was younger. He was abandoned as a kitten and one day say a film about Hollywood. The film showed that Hollywood had a lot of delicious food so he decided to go there. In Hollywood, he is picked up by a group of Meowths, led by a Persian. He meets a female Meowth, Meowsy and wants to impress her. Meowsy only likes humans (plus, she's spoiled!) so Meowth decided that if he learned to walk and talk, Meowsy would like him. Unfortunately, it didn't. Meowsy rejected him for the Persian gang leader and Meowth was heartbroken.
The first word Meowth could say was Rocket which is why he later joined Team Rocket.
Meowth was previously owned by Giovanni but was later replaced by a Persian. He has this all-time goal to please Giovanni though.
Because Persians seem to ruin his life all the time, Meowth has vowed to never evolve.
Meowth gets annoyed easily but is totally cute most of the time. His solution to everything is fury swipes.
And apparently Meowth leaves this little 'mark' of his in all the holes Team Rocket digs. It's a Meowth figure thing in the dirt.