Battousai said everything I was going to suggest XDD
This was a decent demo. Perfect length, nice variety of characters. However, you can make it so much better, with your voice it would be a shame not to make another demo that can really show off your potential! The main thing I think would benefit you is to not imitate characters next time. Create your own characters that have distinctly contrasting tones and pitches.
Throw in some old ladies, boy voices, little kid voices, sexy temptress voices, monotone characters, and outlandish creepy ones -- and of course your normal voice. All the while hitting the extreme emotions (anger/yelling to sad/crying/hysterical) and everything in between. It's a lot to think about, but after a few tries you'll finally get the hang of it! Keep up the great work ^^
Also, to enhance each new voice/emotion, it really helps to use a new song each time ^^