Forum:Tennant tardis reappears

Watching the latest CBBC doctor who trailer I noticed that the old Tardis flew by David Tennant has appeared with Amy and Rory inside it(http://www.bbc.co.uk/doctorwho/dw/videos/p00g5scl). I know that last series someone was trying to make their own tardis (episode : The Lodger) and that the same "tardis" that appeared then has appeared in the new series trailer (http://www.bbc.co.uk/doctorwho/dw/videos/p00cyvpy). One can't help but notice a tardis convention happening on our screens and cant help being curious.