So in the 2007 Christmas special Voyage of the Damned the Tenth Doctor met up with Kylie Minogue in the guide of Astrid Peth, a waitress on the Space Cruiser Titanic. How excited we were over the name being an anagram for TARDIS (and Peth apparently being Welsh for part). What this piece needs to examine is the credentials to raise her to the status of inconstant companion and assess the chance (if any) of a more permanent berth on the TARDIS.
Why the acclaim?
Well the chemistry with the doctor was fantastic and there was a very direct emotional connection made that threatened to lead to a level of intimacy hitherto unheard of. Kylie is of course a super-star and the character is pure companion fodder in that she is bored with her career, highly resourceful and easy on the eye.
Sadly she did die at the end of the story – though fragments of her were set adrift to wander through space.
Chances of a return
At the time there was much speculation that Astrid may return, given though that Kylie has things to do, RTD has moved on and we have a new Doctor the most we might hope for would be the current Doctor potentially meeting Astrid earlier in her life and not giving away her destiny. This probably resembles the River Song plot too closely and so will never happen.
So, Kylie in the TARDIS? We should be so lucky (lucky, lucky, lucky [sic!]).