Lily says that it took 151 years for Herman to reach his 2nd childhood, implying that Herman is 151 years old. This would make Herman's "birthday" 1815, going by the date of this episode's first airing. This is very accurate to the actual date of the creation of the novel Frankenstein. It was in 1815 that Mary Shelley first conceived of the idea, writing begun in 1816, finished in 1817, and published in 1818.
Boris: Boris Karloff
Boris is most likely named such as a reference to Boris Karloff, who became famous playing the Frankenstein Monster for Universal Pictures.