Baron Maigel--Maigel reappears in Chapter 23
"I have just been cut in half" -- the telegram Poplavsky receives is even funnier in Russian, which uses the impersonal form of the verb "zarezat'," which usually means to cut someone's throat, with the tram in the instrumental. The meaning is something like "it has killed/cut me by means of a tram." The construction is almost as bizarre in Russian as it is in English.
"An Apartment in Moscow!": If a Soviet citizen could obtain an apartment in Moscow it was a great victory. Moscow had goods that could not be found anywhere else. However, to gain a permit to live there (propiska) one had to have been born in the city or marry someone with a permit. Poplavsky's attempts to trade his apartment in Kiev for one in Moscow and his desire to inherit his nephew's housing is a common scenario during the Soviet period. See The Housing Shortage.
"Aha!"-- Poplavsky's several exclamations of "Aha!" show that he knows how to interpret the news that the officials have vanished. The man he is talking to is not even identified by name (even his name has vanished, like that of one of the apartment's original residents!), and he gives only evasive answers until he too vanishes.
"to have them all suddenly be" The Russian here puts the men who vanish in the accusative (they are the objects of the action of the unmentionable NKVD) -- but there is neither a verb nor a subject. Poplavsky, clever man that he is, knows what subject and verb are acting.
Valerian drops --distilled from the plant Valeriana officinalis (Heliotrope), these drops are still used as a mild sedative to calm anxiety and the heart. 300 drops would be a huge dose, a coma or death.
funereal cape with a fiery-red lining, sword with a shiny gold hilt--these are costumes and props appropriate to Mephistopheles in Gounod's Faust. On the importance of the opera Mephistopheles see Lidiia Ianovskaia, Tvorcheskii put' Mikhaila Bulgakova, 265-69.
Tails or a black dinner jacket--When Bulgakov and his wife were invited to a reception at the American ambassador's residence, the invitation had a note added: "tails or black jacket." Elena Sergeevna writes, "Misha was worried that the note was meant for him only. And I tried very hard to "create" a tailcoat quickly. But the tailor couldn't find the right fabric and he had to go in a suit." (quoted in Sokolov, BE, 139)
stained-glass windows, church altar cloth--Various houses in Moscow at the turn of the century had stained glass windows, though not the one Bulgakov actually lived in. The church-like atmosphere prepares the reader for the ball/black mass that takes place in chapter 23.
sturgeon that's second-grade fresh--this has become one of the many popular sayings from Bulgakov's novel. It was common in the Soviet Union to classify things into grades. In the 19th century there was an expression--"partially fresh eggs," which may have come from an 1895 Punch illustration by du Maurier: "Partially excellent egg." The sturgeon may be a reference to a line from Chekhov's "Lady with a Dog:" "the sturgeon was a bit off."
ten-ruble gold pieces -- small ten-ruble coins, also called "chervontsy." Many examples here.
the beret meowed and turned into a black kitten--Bulgakov apparently got this detail from Andrei Bely's novel Moskovskii chudak. In it the nearsighted professor Korobkin puts on a cat instead of his fur hat.
in a little white house--Rubanovsky's drugstore was in Bol'shaia Sadovaia 1, and Elena Sergeevna, Bulgakov's wife, lived in the house described as Kuz'min's. (The buildings were torn down when the Hotel Pekin was built.) Kuz'min actually lived not far away, at Sadovo-Kudrinskaia 28.