Not really sure what Justin Bieber is, despite airheads banging on about it constantly on Twitter, but found this - and found it amusing.
Well, Tennant's facial expression anyway. If we could be bothered we'd replace the Bieber panel with one of Tom Spilsbury's giving another run-out to his horrible description of Doctor Who fans as 'dafties'.
Other possibilities: The Huw Edwards bit from Fear Her; anything from New Earth; Cyberwoman; Barrowman on one his awful talent shows; one of Pip'n'Jane Baker's tongue-twisters.
I stumbled across this advert somewhere on the web, which shows Jon Pertwee in what turned out to be his final role - an advert for Vodaphone filmed on Pilgrim Street in Liverpool.
It was an odd situation, as I followed the ad back to Youtube - it had been embedded on someone else's site - and discovered that I'd uploaded it a couple of years ago.
The ad has a special place in my heart as I have lived in Liverpool for most of my adult life and the Great pert was my favourite Doctor. Enjoy.