Besides MorphVox, there is also a program called 'Voxal' (
https://www.nchsoftware.com/voicechanger/index.html)
I used it for a few projects and got some nice results. Even though it's gui was a bit confusing at first, i really like it.
You can load or record wave files and also use it in realtime, as it injects itself into your standard mic input.
As a side note: i initally used a basic headset microphone, but now with a seperate semi-pro mic it works much better (no wonder).