This is the last episode in which Sailor Mercury, Sailor Jupiter, Sailor Mars, Sailor Venus, Luna and Aretims appeared until the series finale.
Rei telling Usagi that they will always be together is a callback to The Sailor Soldiers Die! The Tragic Final Battle (1993).
This is the last episode in which the Sailor Guardians are shown transforming. As such, Usagi transforms into Eternal Sailor Moon for the last time.