I like the snippets of dialogue which refer to different quests, events and so on throughout the game. Such as:
Two asura dreamers in the sylvari tutorial talking to each other – one wants to grab a sylvari and chop up him/her. The other jokes, are you going to experiment or make a salad?
Two asura in Lion’s Arch talking to each other – one makes a deep and thoughtful comment about the sylvari and the other says he was going to make a bad salad joke, but now he doesn’t feel like it.
In the opening of the asura personal story, the Inquest has just finished demonstrating a new invention – the floating grisworl. The same device shows up in the human personal story involving the circus. All the crewes from the different asura personal stories are assembled in the area, including Shrieksy, a raptor that hatches during one of the stories.
In the human “home” instance a guard is talking with a woman who is distraught because her young son hasn’t come back from the circus – if a human toon chose the circus option for the personal story he investigates the disappearance.
These are just some little things I’ve noticed… these little continuity details are all over the place.
