Crossover

jennyaxe had an idea. So, for fact-checking reasons we watched Angel S5:20 "The Girl in Question" while eating dinner. And her idea really fits the canon extremely well.

You remember the guy that Buffy is said to be dating in that episode, the Immortal? Who had been in a pain in the ass for Angel and Spike several times before over a period of centuries? Who had had a threesome with Darla and Drusilla? It's totally Jack Harkness from Torchwood. Everything we hear about him, from appearance to tastes to behaviour, just fits perfectly.