As has been pointed out before, the elderly couple at
Antonina Pavlovna's birthday party, Aunt Zhenya (the sister of Antonina
Pavlovna's late husband) and Uncle Paul, hints at Jean Paul (pen name of
Johann Paul Friedrich Richter, 1763-1825). Jean Paul is the author
of Auswahl aus des Teufels Papieren ("Selections from the Devil's
Papers," 1789, signed J. P. F. Hasus). There is a Doppelgänger in Jean Paul's
novels Blumen-, Frucht- und Dornenstücke, oder Ehestand, Tod und
Hochzeit des Armenadvokaten Siebenkäs ("Flower, Fruit and Thorn Pieces; or,
the Married Life, Death and Wedding of Siebenkäs, Poor Man's Lawyer," 1796-97)
and Flegeljahre ("The Awkward Age," 1804-5).
Alexey Sklyarenko