a real world point of view
In the 1980s, Gareth Jenkins was a child who wrote into the BBC One audience wish-fulfilment programme, Jim'll Fix It, to ask if they could let him star in his own episode of Doctor Who. As a part of the request, he demonstrated that he already had a complete Sixth Doctor's costume.
The producers of Jim agreed, and worked with John Nathan-Turner's staff at Doctor Who to create the sketch, A Fix with Sontarans. Jenkins — and his kid-sized Sixth Doctor's costume —did indeed play a major role in it, opposite Colin Baker and Janet Fielding.
At the conclusion of the episode, Baker presented Jenkins with both a Jim'll Fix It medal and the "meson gun" prop to keep.
Gareth Jenkins, the "character" Edit
Since A Fix with Sontarans so thoroughly breaks the fourth wall, it's difficult to consider Gareth Jenkins a character within the televised Doctor Who continuity — especially since the script called for him to say that he had watched Doctor Who on television. However, it is possible to give a few details about the Jenkins "character".
- He gets transported from Earth to the Doctor's TARDIS by accident.
- He wears a boy-sized version of the Doctor's outfit.
- He knows how to operate the TARDIS' controls from watching the Doctor do so on Doctor Who
- He kills the two Sontarans, because his Doctor Who viewings have told him which switches to press to kill the two Sontarans.
- Group Marshall Nathan says that in the year 2001, when Sontarans invade, the adult Gareth will lead a resistance movement which turned away the invasion fleet.