In the United States, smell copyright is well-established case law. Smells can be copyrighted if they're not a functional part of the product. Perfume no, smell added to shovels to distinguish your brand, sure.
That's interesting, I thought the smell was a result of the ingredients - which would make it non-distinctive and unsuitable for a trademark (as others would be excluded from making the product so the trademark would operate as a perpetual patent).
Maybe the smell is a trademark only for other goods (I don't know what Class Playdoh falls in, toys?), eg Playdoh scented merch?
Edit: Trademark, not copyright, damn it!