'Where's Proffessor Prune?'

'In the Library'

'Where's that?'

'At the bottom of the left trouser leg'

'Well that's a turnup for the books'

Yes indeed, Spot the Dog (played by Tim Brooke-Taylor) was one of the hits of ISIRTA. There was huge audience response whenever Spot spoke (usually a pathetic woof).

But probably nothing at all to do with 'our' Spot, who shares his middle name with lots of famous people.