NPC personality change

Hello!

I once ran a campaign with all PCs having just finished their cadet cruise. So, in order to give them at least some say on their ship I assigned them to an Oberth class vessel (the campaign is set during TNG). I wanted to portray the female, human XO's unsatisfaction with the ships current mission by treating the players a little bit unfriendly.
To make things worse the players had to beam over to a Romulan vessel trough electromagnetic interference. Since transporting humans without pattern enhancers would have been dangerous they decided to beam over pattern enhancers first, before beaming aboard themselves.
After two of them had failed their skill checks the XO took over and succeded brilliantly.
Well, at some point during this first adventure my players seem to have decided that they didn't like her.

I've really tried hard to make the players like her, but whenever I mentioned her afterwards they said "Ah, that's the one who doesn't like us, right?"

Have you ever succeeded in changing a once-formed opinion of your players about a NPC or did you have similar experiences?

Give the XO some leave. Make the temporary replacement even worse. The players thought the old XO was a hard arse, what about the guy who ensures all crew take an 0500 hours PT training, strict mealtimes and head times, enforced 'lights out' policy. Really put them through the wringer.

They will be glad when 'ole' stoneface' returns. After all, they may still dislike her, but she will at least be 'their' hardarse!

Why don't you try to give your players some chance to better understand the XO, instead of changing her behaviour?

Get them in a frustrating situation and then provide them with some convenient crewman to tread unfriendly in case they want to vent some of their own frustrations.

Next time around have another NPC (not the CO or XO, but maybe one of the department heads) give them a friendly lecture about not mistreating people just because you are unsatisfied with something else.
If you really want to drive your point home have this NPC end his little pep-talk with something like "I know sometimes it is difficult not to vent your anger on some innocent bystander. It can happen even to the most experienced COs or XOs." ;)

If they are not completely brain-dead they should get the message. :D

I'm having a similar issue in a non-Star Trek campaign I'm running. It's set in the Farscape universe, and one of the prominent "crew NPCs" is a Hynerian revolutionary. Now of course, the players immediately associated him with Rygel from the show (if you've never seen the show, Rygel's short, materialistic, self-centered, thieving and sneaky. And he used to be Dominar of an interstellar empire!) My NPC does bear a resemblance to Rygel, in the way of mannerisms, but I wanted him to come across as more honorable. So, I emphasized some of his positve aspects -- he's very fair and reasonably honest with the PCs, and he has a cause in which he earnestly believes.

Allow some other aspects of the NPC that encourages the crew to sympathize with her on something. Maybe introduce a mission in which one of the XO's family members is in danger, and let the NPC show her feelings for it. If you really want to go all-out, have the family member die at the end of the episode, and portray how it effects the XO. If you do it right, the PCs will get to see a side of their commanding officer they don't normally see, and it should soften their opinions of her.

Another way I can think of is to through the PCs in a situation where they have to save the XO's life by working together -- something like the XO leads a landing party consisting of the PCs, and then gets incapacitated. It's up to the PCs to find a way to contact the ship and get her medical attention before she dies. You may be able to get the players to "bond" to the XO in the course of the crisis.

It sometimes takes time to endear an NPC on your players... it's probably a good sign that they have a strong opinion at all about her. :)

Thanks for all the good advice posted so far. I had also once thought of letting the PCs save the XO, but I had forgotten it before I've written it down. I' really getting old :) !
I especially like the idea of Dan, probably because it's so mean that no one would expect me to confront them with such a situation.
But combining the "hard arse superior officer" and "rescuing the XO" ideas will probably make them loving her.