Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
In VN’s novel Zashchita Luzhina (“The Luzhin Defense,” 1930) Kurt and Karl (the German revelers) mistake Luzhin who fainted in the street after his game with Turati for their friend Pulvermacher:
Describing Cincinnatus’s childhood in his novel Priglashenie na kazn’ (“Invitation to a Beheading,” 1935), VN mentions malina (rumpberry) and tych’ (poke) among the games that Cincinnatus played with other children:
In VN’s novel Zashchita Luzhina (“The Luzhin Defense,” 1930) not a single date is mentioned. But we can figure out at least three exact dates: Luzhin's birthday, the day on which the action in the novel begins and the day of Luzhin's death. Luzhin was born on October 19, 1902, goes to school on Monday, August 31, 1909 (OS), and dies on February 21, 1929.
In The Luzhin Defense, the English version of his novel Zashchita Luzhina (1930), VN renames Mit’ka (the boy of the lady from Russia) Ivan:
In VN's play Sobytie ("The Event," 1938) the action takes place in the morning, in the afternoon and in the evening of one and the same day (the fiftieth birthday of Antonina Pavlovna Opoyashin, the lady writer):
In VN's play Sobytie ("The Event," 1838) the action takes place at the end of the summer, on the fiftieth birthday of Antonina Pavlovna Opoyashin (the lady writer):
Входит Антонина Павловна Опояшина, мать Любови, с пестрым мячом в руках. Это аккуратная, даже несколько чопорная женщина, с лорнетом, сладковато-рассеянная.
Антонина Павловна.
Здравствуйте, мои дорогие. Почему-то это попало ко мне. Спасибо, Алеша, за чудные цветочки.
Трощейкин (он не поднимает головы от работы во всю эту сцену).
In VN novel Ada (1969) Van tells Ada that he would like to be a goblin-sized Gulliver in order to explore her mouth:
Describing Shade’s murder by Gradus, Kinbote (in VN’s novel Pale Fire, 1962, Shade’s mad commentator who imagines that he is Charles the Beloved, the last self-exiled king of Zembla) quotes a line from Matthew Arnold’s poem The Scholar-Gipsy (1853):
The narrator and main character in VN’s novel Ada (1969), Van Veen is the author of Letters from Terra, ‘a philosophical novel:’
Ada’s letters breathed, writhed, lived; Van’s Letters from Terra, ‘a philosophical novel,’ showed no sign of life whatsoever.
(I disagree, it’s a nice, nice little book! Ada’s note.)
At the beginning of VN’s novel Zashchita Luzhina (“The Luzhin Defense,” 1930) bystroe dachnoe leto (a swift country summer) and neveroyatnaya karikatura (the unbelievable caricature) are mentioned: