Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
In his letter to Ada, written after Lucette’s suicide, Van Veen (the narrator and main character in VN’s novel Ada, 1969) uses the phrase “entered the picture” (and then repeats it in a slightly different form):
Ada:
In VN's novel Lolita (1955) Humbert Humbert is afraid that his wife Charlotte will bundle off Lolita to St. Algebra:
There was a woodlake (Hourglass Lake - not as I had thought it was spelled) a few miles from Ramsdale, and there was one week of great heat at the end of July when we drove there daily. I am now obliged to describe in some tedious detail our last swim there together, one tropical Tuesday morning.
Describing his professional dreams, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions a typo on every page and coins the word ‘skyscape:’
What are dreams? A random sequence of scenes, trivial or tragic, viatic or static, fantastic or familiar, featuring more or less plausible events patched up with grotesque details, and recasting dead people in new settings.
Describing his novel Letters from Terra, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions the corpuscles of his bloodstream and a Mr Nekto’s ripe boil newly lanced in Nektor or Neckton:
According to 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), Shade began writing Canto Two of his poem on July 5, 1959, and on the same day Gradus (Shade’s murderer) traveled from Onhava (the capital of Zembla) to Copenhagen:
Line 181: Today
According to 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), in his country the Skye terrier is called "weeping-willow dog:”
Describing the King’s escape from Zembla, 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) mentions the nippern (domed hills or "reeks"):
Describing the King’s escape from Zembla, 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) mentions the nippern (domed hills or "reeks"):
Describing the King’s escape from Zembla, 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) mentions the green, gray, bluish mountains – Falkberg with its hood of snow, Mutraberg with the fan of its avalanche, Paberg (Mt. Peacock), and others:
Describing the King’s escape from Zembla, 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) mentions the green, gray, bluish mountains – Falkberg with its hood of snow, Mutraberg with the fan of its avalanche, Paberg (Mt. Peacock), and others: