This episode was based on Act 2 of the manga. Episode 8 of the anime was based quite closely on this manga chapter. In the anime they added lots of filler in between episodes 1 and 8, where Usagi fought on her own. Most of it was pretty boring... in fact, I'd say that was one of the low points of the entire anime series. Thankfully, PGSM sticks much more closely to the manga's pacing, and Sailor Mercury's introduction is in episode 2. This episode of PGSM also had the introduction of the secret meeting room at Karaoke Crown, which in a way is similar to the secret computer room at Game Center Crown that was introduced in Act 6 of the manga.

The main point of this episode, in all three versions, is Ami becoming Sailor Mercury. All three versions also include Usagi making friends with Ami (or trying to), and the idea of the Dark Kingdom stealing energy from the students at Ami's juku (cram school). However, beyond that the live action version is wildly different from the anime and manga versions.

The story in the anime and manga involves lots of kids signing up to Ami's juku, where a monster from the Dark Kingdom is using a special "crystal disk" in the computers that drains people of their energy. Only Ami is safe because she hasn't been using the computers to learn. Usagi arrives and uses her newly-received transformation pen to turn herself into a doctor (why a doctor is not entirely clear), and then there is a battle at the juku (which in the anime involves the monster asking Usagi questions).

In PGSM, on the other hand, the monster (which has possessed the teacher) uses sound waves to steal people's energy, and Ami is immune because she is listening to the Minako Aino minidisc that Usagi gave her (Ami and Usagi's shared like of Minako's music is, of course, original to PGSM). The battle then takes place in the mall where the juku appears to be located. Incidentally, the anime has Sailor Moon defeat the monster (which by this point has left the human it had possessed) using Moon Twilight Flash. This becomes Sailor Moon's standard attack for defeating monsters, and arrives with little fanfare, unlike in the manga.

Other things that didn't make it into this episode of PGSM are Ami playing the Sailor V arcade game (really well), Mamoru noticing Luna talking, and Tuxedo Mask rescuing Sailor Moon a second time.

Ami is generally the same character - her intelligence is well above average, and this has led to her being somewhat isolated from other people. However, this isolation is emphasised much more in PGSM. First of all, the fact that Ami spends a lot of time alone because her mother is a doctor and isn't at home a lot is brought up in PGSM as a significant point, which it never was really in the manga or anime, and certainly not this early on. Also, in this version, Luna tells Usagi well in advance of the battle that Ami is a Sailor Guardian. Usagi tells Ami this, and Ami believes that the only reason Usagi wants to become Ami's friend is because she is a Sailor Guardian! Although Ami is happy to fight as a Guardian, she does not instantly become very good friends with Usagi, as she does in the manga and anime. In fact, she continues to be very insecure about being Usagi and Rei's friend for several episodes after this. In my opinion this is a major improvement - I find it much more interesting and realistic for Ami to be a character who develops over time.

Finally... That monster, and those twirls. The manga and anime mostly used monsters that looked similar to humans, but uglier. PGSM, on the other hand, seems to have taken a cue from Power Rangers in its monster design. This isn't all that surprising - PGSM is made by Toei, the same company that produces the Super Sentai series that Power Rangers are adapted from. At the same time, some of the monsters are really quite silly, and it wouldn't have been hard for them to have made them more ordinary-looking. I won't mention the monsters in every comparison, but be aware that the monsters were rarely that silly in the Dark Kingdom arc of the anime. The Dead Moon Circus arc, on the other hand... (The manga had far fewer monsters in general, but those didn't look like Power Rangers monsters either.)

The other thing I'll mention here is the fighting style used by the Sailor Guardians. In the manga, there was very little combat outside of the special attacks, which works when the action scenes only need to be a few pages long. In the anime they tended to get thrown about by the monster for a bit (depicted using still shots), and then they used their special attacks. In PGSM, they twirl about like ballerinas for a bit, apparently doing nothing but moving around, and then they use their special attacks. This doesn't really bother me - it makes sense that they rely on their attacks rather than on punches and kicks, and they need to avoid the monster long enough that they have an opportunity to attack. Still, lots of people think that the action scenes are quite badly directed in PGSM. (They do get better as the series goes on, however.)