Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
Describing the patio party on the next day after his arrival in “Ardis the Second,” Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions G. A. Vronsky (the movie man who makes a film of Mlle Larivière’s novel Les Enfants Maudits) sipping his vodka-and-tonic:
Describing Demon’s visit to Ardis in the summer of 1888, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions dead Demon’s ‘crimes’ about which Marina used to ramble on in the late Eighteen-Nineties:
Describing Ardis Hall, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions an old ‘jikker’ or skimmer, a blue magic rug with Arabian designs:
Describing the death of his, Ada’s and Lucette’s mother Marina (the twin sister of Demon's poor mad wife Aqua), Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions three elements (fire, water and air) and uses the word naperekor (in spite of):
Describing Villa Venus (Eric Veen’s floramors), Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions Cherry, a little Salopian of eleven or twelve:
Leaving Ardis forever, Van Veen (the narrator and main character in VN’s novel Ada, 1969) recalls Ada’s favorite tree, Ginkgo biloba:
‘The express does not stop at Torfyanka, does it, Trofim?’
‘I’ll take you five versts across the bog,’ said Trofim, ‘the nearest is Volosyanka.’
His vulgar Russian word for Maidenhair; a whistle stop; train probably crowded.
Describing the conversation about religions in “Ardis the First,” Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions the plough team (as Van calls himself and Lucette):
‘When I was a little girl,’ said Marina crossly, ‘Mesopotamian history was taught practically in the nursery.’
‘Not all little girls can learn what they are taught,’ observed Ada.
‘Are we Mesopotamians?’ asked Lucette.
Among the doctors (all of whom bear names connected with rabbits) in VN’s novel Ada (1969) there are Doctor Krolik (Ada’s beloved teacher of natural history whose name means in Russian “rabbit”) and the German gynecologist Seitz (whose name sounds like Russian zayats, hare):
Before the family dinner in “Ardis the Second” Demon Veen (in VN’s novel Ada, 1969, Van’s and Ada’s father) calls Blanche (a French handmaid at Ardis) “a remarkably pretty soubrette:”
In VN’s novel Ada (1969) Van and Ada find out that they are brother and sister thanks to Marina’s old herbarium that they discovered in the attic of Ardis Hall: