There seems to be a large flaw with the BBC iPlayer, their Parental Control feature is based on a cookie.
This makes it very easy for any computer whiz kid to allow themselves to watch programmes which are normally shown after the watershed whenever they like. And to top it off, the BBC explain how to delete the cookie in their help page.
2016 Edit turns out this page is rather high on a Google search. This post was first written in 2007 for the web version of the iPlayer. If your TV is asking for parental control it’s most likely due to the TV’s built in restrictions. If you’ve yet to set a PIN, it will tend to be 0000, 1234 or 1111. If these don’t work search for “default code” along with the make and model of your TV in Google.