Sailor Mercury's uniform has shoulder pads, which is not the case at any point in the original series.
Queen Beryl makes her debut in this episode. In the original series, she made her debut in the first episode.
In her original debut episode, Sailor Mercury uses Bubble Spray against the Youma. In this episode, she uses her Mercury Aqua Mist attack instead.
Usagi and Luna did not realize that Ami was a Sailor Guardian until near the end of the episode, amidst the battle with the youma. They were initially suspicious of her and thought she might have been from the Dark Kingdom.
Yumiko, Kuri, Tuxedo Mask, and Rei all made appearances in this episode, which did not occur in when Sailor Mercury debuted in the original Sailor Moon (1992) anime. Although Mamoru did appear in the original episode, he did not appear as Tuxedo Mask.