When the Lab members are deciding on the past mail name, Daru votes as "The mail who leapt through time", which is in fact a reference to an anime title called "The girl who leapt through time". In turn Mayuri votes as "Back to the mail", which is a reference to the movies "Back to the Future", and afterwards "DeLorean mail" as a reference to the Doc's car from the "Back to the future" movies.