Aww. I love that. One of my cats did that as a kitten and never grew out of it. She's five now and still has the cutest little 'mew' instead of a real meow.
Thats how my Mew got her name! Lol well originally it was after the Pokemon, but it was too cute when our 6 year old daughter said, "What's your name?" And the little kitty would say, "Mewwwwww!"