In a letter of about/not later than June 27, 1834, to his wife Pushkin calls Smirnov, whose wife just gave birth to twins, krasnoglazyi krolik ("a red-eyed rabbit"):

Какова бабёнка, и каков красноглазый кролик Смирнов?

Smirnov's wife was a close friend of Gogol (who feared that he will be buried alive*). In the 1840s Gogol spent a few summers in Kaluga as a guest of A. O. Smirnov whose husband ("krasnoglazyi krolik") was a governor of Kaluga (see Veresaev, Gogol in Life).

Ada, wearing an unfashionable belted macintosh that he disliked, with her handbag on a strap over one shoulder, had gone to Kaluga for the whole day - officially to try on some clothes, unofficially to consult Dr Krolik's cousin, the gynecologist Seitz (or 'Zayats,' as she transliterated him mentally since it also belonged, as Dr 'Rabbit' did, to the leporine group in Russian pronunciation). (1.37)

In a letter of September 8, 1891, to Suvorin Chekhov compares Tolstoy's Afterword to The Kreutzer Sonata to "The Letters to the Governor's Wife" (as Chekhov contemptuously calls Gogol's "Selected Passages from the Correspondence with Friends," 1847):

Толстой отказывает человечеству в бессмертии, но, боже мой, сколько тут личного! Я третьего дня читал его "Послесловие". Убейте меня, но это глупее и душнее, чем "Письма к губернаторше", которые я презираю. Чёрт бы побрал философию великих мира сего!

Tolstoy is the author of "Resurrection" (1899).

It is Greg Erminin who tells Van that Dr Krolik also loved Ada:

'Ah, those picnics! And Percy de Prey who boasted to me about her, and drove me crazy with envy and pity, and Dr Krolik, who, they said, also loved her, and Phil Rack, a composer of genius - dead, dead, all dead!' (3.2)

Greg's twin sister Grace Erminin married a Wellington (2.6). Erminia was the nickname of Pushkin's friend Eliza Hitrovo, Kutuzov's daughter (mother of Dolly Fickelmont, née Tiesenhausen) who was hopelessly in love with Pushkin (see Veresaev, Pushkin in Life). In a letter of May 9, 1834, to her daughter Olga (the poet's sister) Nadezhda Osipovna Pushkin (the poet's mother) mentions Erminia.

In his poem Pered grobnitseyu svyatoy / Stoyu s ponikshey golovoy... ("In front of the sacred tomb / I stand with hanged head..." 1831) Pushkin says that rapture lives in Kutuzov's coffin: "v tvoyom grobu vostorg zhivyot!" On the other hand, Pushkin is the author of Vertograd moey sestry... ("My sister's garden..." 1825). This poem brings to mind Miss Vertograd, Demon's librarian (1.21). In a letter to Ada Dr Krolik (who was to die in his garden) mentions Miss Vertograd:

Finally, Ada showed Van a letter from Dr Krolik on the same subject; it said (English version): 'Crimson-blotched, silver-scaled, yellow-crusted wretches, the harmless psoriatics (who cannot communicate their skin trouble and are otherwise the healthiest of people - actually, their bobo's protect them from bubas and buboes, as my teacher used to observe) were confused with lepers - yes, lepers - in the Middle Ages, when thousands if not millions of Vergers and Vertograds crackled and howled bound by enthusiasts to stakes erected in the public squares of Spain and other fire-loving countries.' (1.21)

The name Philip Rack (of "a composer of genius," as Greg Erminin calls him) seems to hint at the Spanish Inquisition.

*from Gogol's "Testament" (1845): Завещаю тела моего не погребать по тех пор, пока не покажутся явные признаки разложения. Упоминаю об этом потому, что уже во время самой болезни находили на меня минуты жизненного онемения, сердце и пульс переставали биться... Будучи в жизни своей свидетелем многих печальных событий от нашей неразумной торопливости во всех делах, даже и в таком, как погребение, я возвещаю это здесь в самом начале моего завещания, в надежде, что, может быть, посмертный голос мой напомнит вообще об осмотрительности. Предать же тело мое земле, не разбирая места, где лежать ему, ничего не связывать с оставшимся прахом; стыдно тому, кто привлечётся каким-нибудь вниманием к гниющей персти, которая уже не моя: он поклонится червям, её грызущим; прошу лучше помолиться покрепче о душе моей, а вместо всяких погребальных почестей угостить от меня простым обедом нескольких не имущих насущного хлеба.