An all right movie, interesting because I haven't actually been exposed to much Scooby Doo in my life. I remember the cartoons being on Saturday mornings when I was a kid, and toward the end of the time TBS was still showing cartoons I watched a few of the episodes with Scrappy Doo Puppy.
I never understood why Scrappy Doo was added in the first place. Scooby can speak very good English for a dog and Scooby Doo doesn't need Scrappy showing him up with his perfect speech.
The lesson about being exactly who you are was a nice bit of Hollywood propaganda since they're mainly the ones in charge of making sure everybody thinks, dresses and acts the same.