Wendy's Dream Meetings are a series of events where, when going to sleep, Eric(a) ends up being drawn into a dream of a bedroom with Wendy in it. The first of these two meetings are mandatory to progress the story, but the latter two meetings are optional. Each dream must be progressed through sequentially. Each dream offers differing benefits in addition to the story elements.
First Dream
The first dream will happen after having beaten two magicos.
In this first dream, Wendy is first introduced and is unnamed, being known simply as "???". Here she will give Eric(a) a make-up case before they wake up shortly after, leaving the dream. Upon waking, Eric(a) finds the make-up case has appeared in real life as well, and is physically unable to talk about Wendy at all to Natalie, instead having to say Isabelle gave them the make-up case for lack of any other explanation.
The make-up case allows for Eric(a) to magically put on their Magical Girl outfit instead of having to manually put it on. The clothes are now also a true Magical Girl outfit, granting +100 MHP to Eric(a).
Note that since this is where Wendy is initially introduced, this event is required in order to get the prompt to learn Lovely Barricade during the battle against Veronica in the Tomb of Garak. It is therefore technically possible to not get that prompt if the player only beats the Slime Princess, then after freeing the Magical Girl in the Ruined House goes directly to the Tomb of Garak without defeating a second magico first.
Second Dream
The second dream will happen after having beaten three magicos, and after at least five days have passed. This means it will happen the night after the Medical Exam.
The dream starts off with mention about how the Medical Exam went, Eric(a) incensed about the Penis Reduction Transformation if the magical potion was used. Some exposition is given about Wendy, about how she woke up here with a bunch of fragmented memories, but even she is not sure who she really is. Wendy claims to be worried about Eric(a) and their lack of power compared to a true Magical Girl, and gives them the Emerald Rod with directions to head to Phyre's Tower where they can grow stronger through the process of Core Siphoning. Before waking, Wendy asks for a name from Eric(a), still having been only called "???" up to this point, allowing the player to name her whatever they wish.
Third Dream
The third dream will happen after at least two cores have been siphoned.
Upon appearing in the dream room, Wendy is seen at the door, frustrated at being unable to open it. She is shortly after surprised to find Eric(a) there, not being responsible for bringing them here this time. Instead, the magic from siphoning cores is supposedly awakening the power within Eric(a) which was responsible for this. This awakening power also manifests as a new skill, Aurora Glow.
Wendy will now ask Eric(a) to open the door in their mind themself, as that should be something they are capable of which Wendy as an outsider is not. Wendy offers to share some of her power if they do, but Eric(a) is hesitant about letting an unknown person having access to more of their mind. The choice is left in the player's hands. If the door is opened, then the skill Mana Burst will be learned. Note that even if the player chooses not to open the door now, it will open on its own if six cores are siphoned, giving Mana Burst then as well.
Fourth Dream
The fourth dream will happen after the Earth trip, and also requires the dream door to have been opened. If the player declined to open it during the third dream, then siphoning six cores will achieve the same effect. Rather than being guaranteed to occur after the conditions are met, the fourth dream has a chance to trigger depending on the progression of events with Yoshida. If Yoshida has not yet stolen any cores, then there is a 33.3% chance to trigger each note, 50% chance with one core stolen, and 100% if two or more cores have been stolen.
With the door in the dream being opened, Eric(a) and Wendy decide to go see what lays beyond, Wendy not having gone to check by herself yet. Beyond the door awaits a copy of Eric's original room back on Earth. Of particular note is a rather conspicuous treasure chest in the middle of the room. There are also some additional female articles of clothing that are out of place compared to how his room originally would have been. The dress on the right is of no consequence, but the underwear on the left are the See-through Underwear which can be acquired. It requires the Panty-Wearer Transformation in order for the player to have the option to pick them up, the second stage of which will automatically make Eric(a) pick them up. Not having the transformation or choosing not to pick them up will make them disappear. Picking them up, in addition to gaining them as an accessory, will give an acceptance point.
Inspecting the treasure chest will have Wendy explain that it is a seal on some of Eric(a)'s memories, along with some speculation that her own presence in their mind may be related. The player is given the choice on whether or not to risk opening the chest. If the chest is opened, then the player will be taken to the optional dungeon Eric(a)'s Memories. Choosing not to open the treasure chest will have Eric(a) simply waking up. Going to sleep in the future will have the same chances as before to trigger the dream, giving the player the option to return and open the chest at a later date.