Oscar the Grouch Phone

I haven't a clue as to how voice-changing stuff works, so please correct me if I mess this up big time. If you could record your voice, and get it changed into something like robot, or mouse, like they do with those voice recorders you get in joke shops, why not Oscar the Grouch (from Sesame Street)? If I got called by those annoying people who try to sell us new kitchens/holidays on the moon, I could just call for my 'dad', put the Oscar voice changer on, and tell the cold caller to f*ck off, or I'll call the police. The thing about Oscar the Grouch is that he sounds really creepy. This would help when I get those morons who think I'm 27...

And if I ordered 25 pepperoni pizzas with anchovies to the neighbours house...