I heard some people have rubber duck fetish

Depends on the age and specifics. When I was growing up it wasn't uncommon for kids to have a pocket knife (usually smaller and less "tacticool" than that) for cutting rope, branches, etc. That razor is also probably better suited for an older child, but a safety razor or exacto knife was often given to kids for hobbies like model building. At least in my case though it had to stay in the work area and you had to follow very strict safety rules or else you'd lose that and other privileges. It looks like just a staged joke though, but I did know kids to do some messed up stuff like that so I can't say it isn't real- the "parents reaction" though makes me think it's likely fake.

Perhaps the person is raising a Kinky Child.