Freds voice changer???????

what program does fred use to change his voice??, dont say he says stuff slowly then puts it high pich, coz it still sounds wierd, and he doestn speed up his voice coz everything around him is normal, and it sounds like he just swallowed hielian or sumthing, so plz if u know plz put the link in so i can download it or sumthing, or just tell me