Message #76063

[Jamdog]

Star Trek has plenty of inspiration for a companion, could also look to:

Seven of Nine:  A companion who used to be cyborg (*cough* 'cyberman') but was separated to recover their humanity
Spock/Tuvok: A human-looking race that shows no emotion and embraces logic
Garak: A seemingly innocent tailor, but you know he has a chequered past, lofty connections and his finger in far too many pies...
Q: An omnipotent presence who can cause planets to explode by clicking their fingers.  May not work well as a companion though...
Klingon: A noble warrior race that distrusts anyone else.

Personally, I can't see a Klingon on the TARDIS would work, but the top 3 above all have possibilities...