Post a comment to this post claiming your favorite non-Companion. You'll have eight weeks from the moment your name goes on the list to produce a story or a piece of fanart showing an alternate reality in which your non-Companion travelled with the Doctor*. If you can't pull it together within that time frame, no worries, but you will lose your exclusive claim on said character. Further rules, none of which are difficult, can be seen here.
* It is preferable though certainly not required that your non-Companion travel with the Doctor s/he met canonically. For instance, it would be nice to see Duggan travelling with the Fourth Doctor, not the Tenth.
Will Chandler from "The Awakening" -- ianthekid (03-13-07)
Chela from "Snakedance" -- pallasathene87 (03-07-07)
Duggan from "City of Death" -- lizbee (03-07-07)
Jane Hampden from "The Awakening" -- meegat (03-05-07)
Mrs. Moore from "Return of the Cybermen" -- cryptile (03-10-07)
Pex from "Paradise Towers" -- jedi_penguin (03-05-07)
Zach and Ida from "Satan's Pit" -- doyle_sb4 (03-05-07)