Response to this prompt from the Into Darkness kink meme: (Mind the spoilers)
That tribble kind of saves Kirk's life, amirite?
Spock adopts it.
The Enterprise was fully repaired and they were underway in their new five year mission by the time Jim thought to ask about the Tribble. Honestly he had given little thought to it after finding out how Bones had figured out that Khan's blood could revive him. As it was he only remembered it thanks to a report from a nearby Starbase saying they finally were able to get a Tribble break out under control.
The Captain sat back in his chair on the bridge after reading the report and with a thoughtful look glanced around at the crew members as if he would get the idle curiosity solved by just looking. After noticing that Spock was still not back on the bridge after being called to the labs for a brief look at some experiment, Jim turned to face Sulu. Most wouldn't know about it but the Helmsman was surprisingly well informed of any gossip around the ship. Jim suspected it was because of Chekov but had no proof just yet.
"Mr. Sulu, you happen to know what happened to the Tribble Bones was experimenting on?" He asked with a smile, sure that the other man would know. Instead he was surprised to hear Sulu respond with "No Captain." and a slight shrug. Jim blinked then looked over to Chekov who had turned to Sulu at some point. "What about you Mr. Chekov?" The teen genius shook his head with a look that reminded Jim of a puppy denied a treat. "No Keptin, I haven't heard anything about it."
Huh. Well now the idle curiosity was growing with each none answer. Jim turned to Uhura next. "Is it the same for you Lt.?" She gave a nod as she stopped reading some past scans. "Yes Captain." Jim turned to look at the view screen and slumped a bit in the chair even as he pressed the button to com Bones. "What is it? Did someone get hurt?" Came the mildly disgruntled voice of McCoy. "Nah Bonce, just got a question for you." Jim said with a grin. A sigh of pretend exasperation could be heard. "Spit it out then Jim as this paper work wont write it's self." The grin on Jim's face grew at the fond tone in his friend's voice.
Even preoccupied with the conversation with Bones, Jim perked up and gave a friendly smile when Spock arrived back on the bridge. "What ever happened to the Tribble you tested Khan's blood on?" There was silence over the com for a few seconds before McCoy responded, causing Jim to miss Spock quirking an eyebrow at the question. "You're asking that now? Once it was clear the Tribble would live thanks to the blood I passed it off to an Ensign. I'm a Doctor not a pet owner and I have no time for a Tribble." While that didn't fully answer his question on what happened to the sentient ball of fluff, Jim had to laugh at the Doctor's grumble. "Really? I would have pegged you for a dog person, Bones." The Captain teased. More grumbling could be heard for a minute before Bones said, "I'm getting back to this damn paper work, stay out of trouble." and signed off.
Jim chuckled then turned to find Spock looking at him with a raised eyebrow. "Was there something you needed the Tribble for Captain?" The second in command asked. Jim shook his head and idley tapped the armrests of the chair. "No Mr. Spock, just asking from curiosity." To Jim it looked like Spock was about to tell him something but didn't so the Captain tilted his head and asked, "Mr. Spock?"
Finally Spock opened his mouth and responded, "Kirkleton is currently with in my rooms in the special habitat I made for it."