I wrote Tuf Voyaging (Science fiction by George R R Martin) x Highlander (1992 tv drama) crossover fanfiction.
Here is the summary:
Methos has spent five thousand years surviving—outliving empires, wars, and lovers, always running before anyone could matter too much. Sneaking aboard a starship should have been just another escape. Instead, he finds himself on the Ark: a vessel of cats, order, and the impossibly formal Captain Haviland Tuf.
Tuf speaks in careful precision, Methos in irreverent sarcasm. One clings to order, the other thrives in chaos. Yet as they voyage from one crisis to the next, something shifts—companionship sparks where neither expected it, and survival begins to mean more than just outlasting.
Among Stars and Strays is a tale of banter, cats, and improbable harmony, where an immortal trickster and an ecological engineer learn that even eternity can feel less lonely when shared.
You can read the story on fanfiction archive here:
https://archiveofourown.org/works/71865831
Here is the summary:
Methos has spent five thousand years surviving—outliving empires, wars, and lovers, always running before anyone could matter too much. Sneaking aboard a starship should have been just another escape. Instead, he finds himself on the Ark: a vessel of cats, order, and the impossibly formal Captain Haviland Tuf.
Tuf speaks in careful precision, Methos in irreverent sarcasm. One clings to order, the other thrives in chaos. Yet as they voyage from one crisis to the next, something shifts—companionship sparks where neither expected it, and survival begins to mean more than just outlasting.
Among Stars and Strays is a tale of banter, cats, and improbable harmony, where an immortal trickster and an ecological engineer learn that even eternity can feel less lonely when shared.
You can read the story on fanfiction archive here:
https://archiveofourown.org/works/71865831