I'm not sure if I grasp the exact details of your desired result, but I'm guessing that you want your MC to walk to the tile in front of the door, then have the NPC walk forward and say something to them (or push them perhaps?), then have the player move through the door. If so...
Set the Tile in front of the door to "Event Touch." When your MC reaches the tile, the event will activate.
Then, Select "Set Event Location" (Tab 2) to wherever you want the NPC to come from. I would make sure it's offscreen so the NPC doesn't appear from thin air.
Activate Self-Switch A
Then, start on the next tab of the event. Make sure the checkbox on click "self switch A is ON"
In this event page, change the event graphic to the graphic of the NPC.
The event should be "Autorun."
Set the NPC move route to the space you wish it to go (Next to the actor? In front of the actor? etc.)
Then, type the text you wish the NPC to say. If the NPC is in the character's way, make sure you set the move route again to get it out of the way.
Insert MC's witty retort if applicable.
Next, put Self Switch B On.
Make a new tab. Make sure the checkbox on click "self switch B is ON" and that you change the switch letter to B, as it will automatically set to A.
Next, change the character's move route so that they move onto the door space and arrive in the next room (insert door sound effects if you want; you can find most of this in the quick event door script). Change the trigger to "Autorun." If the player is farther than one tile from the door, alter the move route as necessary.
Finally, put self switch C on at the end of this. Open the tab and paste nothing into it to make sure the cutscene stays over.
...or at least, that's how I would do it.
Hope this helped!