This was basically a 2 person game show in which the contestants had to pre-empt how disasterously stupid celebrities were.
A phrase was read out with one word missing. The celebs had to write down the word they thought would best fit into the gap.
Then, the contestants had to say what word THEY thought would fit, and for every celeb that had the same word, they got 1 point.
As an example, try the following Blankety Blank phrase...
"One-Eyed Jack was well known for having a wooden 'blank' "
Now, we all know that the word LEG would fit in perfectly there, don't we? So we'd say LEG. The presenter would now stroll across to the celebs to see if they had put the same, obvious answer.
Apparently not, though. They'd have words like "EYE" written down, and "CRUTCH" and stuff.
So the majority of people went home with a Blankety Blank checkbook and pen. Yippee!