The Happy Masked Salesman has a very creepy voice. Almost as if he isn't human at all. He has a slightly higher voice and tends to giggle a lot as he talks. I would also recommend attempting his laugh in your audition, as there is a large chance his character does it in the dub. It is apparent that this character has characteristics of being insane as well, so keep that in mind while working on deciding what kind of voice to use.