Why am I a chipmunk?
Well, I have heard stories about, hmmm, around full moon I think, that people turn into some strange creatures, like something wolf-alike.
Now, in this case, maybe it's "just a little too much moon-shine"...
(I have heard people start talking funny in those circumstances)
Sorry, I couldn't help it, you see:
It would be nice if you informed about a couple of things, like
1. Project settings
2. How and to what format the actors were recorded.
Give info about those two, and somebody may be able to guide you to better results than what you currently have.
EDIT: Harm is faster, follow his link as well.
Anyone know what I'm doing wrong?
You did nothing wrong. Your actors, as a practical joke, were high on helium that day.
Welcome to the forum.
The likely culprit is you source Audio. What is it? Since your other Audio is fine, go to the source for you AV file. G-Spot will give you info to help us help you. Likely, you'll have to convert that Audio to "straighten it out," unless "sound like chipmunks" is in the script.
I do have to admit that I really liked some of the other suggestions as to the causes!