Enterprise gets a new crewmember

[Narsil]

Due to a mild change of heart somewhere in the mind of a random Time Lord, the Second Doctor's trial ends slightly differently. Instead of being exiled to Earth in the 20th century, he is put aboard the USS Enterprise NCC-1701-D some short time before Best of Both Worlds. He is in current possession of his TARDIS, yet it is inactive as per the exile, and we'll assume he's accepted as a crewmember. He's also forced by the Time Lords to regenerate into his third form, as per the original term of the exile.

With all this in mind, the Doctor is present aboard the Ent-D, up until he is eventually given control of his TARDIS once again after the events of Parallels. After which, he'll still be aboard the Enterprise for every one of two episodes afterwards. (Sub Rosa, Thine Own Self, Eye of the Beholder, etc.) But he is definitely present for All Good Things due to the heavy temporal nature of that episode.

He's also present for all of the TNG-era films, except that (assuming he hasn't done so already) he'll have undergone the ultimate regeneration into his Fourth form.

Now; what happens differently for the crew of the Enterprise? Do things go better? Worse? Just plain different? Does the storyline take a different course entirely?

[Roondar]

From what I've seen on Dr. Who... I think that many more people will end up dead. Though he never means too, he usually manages to get a ton of trouble down on whoever he ends up near.

Trouble being 'everybody dying somehow'...

And FYI, I love Dr. Who :)

[Narsil]

Well, he did manage to preserve most of UNIT, but yes, he does tend to attract trouble.