IT'S A MIRACLE! That's right... ACTUAL PLOT FROM THE MANGA!

But only for about a minute. Before and after that, it's PGSM-original all the way. (Not that I don't love the series anyway, of course.)

Anyway, Usagi finally finds out that Mamoru is Tuxedo Mask, as happened in Act 7 (!) of the original manga. This still beats the anime, where she didn't find out until Episode 34.

It happened differently in all three versions: In the manga, he rescued her after a battle and took her to his house, where she woke up to see Mamoru wearing only half of the Tuxedo Mask costume, with the rest nearby. In the anime, the two of them were trapped together by Zoisite. After Sailor Moon transformed in front of him, he transformed in front of her. In PGSM, she realises when she says the exact same thing to her, in the exact same way, as Mamoru did earlier in the episode. She then removes his mask and sees his face. (Rainbow pointed out that this is a lot like Episode 148 and Episode 149 of the anime, in Sailor Moon SuperS, where Fish-Eye figures out Usagi's identity in pretty much the same way.)