Emma is a shark-like monster Lightner residing in Hometown. She works at the police station alongside Undyne and Napstablook but doesn’t consider herself a “real officer”, instead handling the more clerical work like processing reports and taking calls.

She is one of the only friends of the Ghost/Blook family and it is implied she only began working at the police station to try and cheer up Napstablook. She also seems to have some history with Undyne as she mentions she and Undyne went to “school” together (though this could also just be a fish joke).

Given how introverted/agoraphobic the Ghost family is, Emma will sometimes deliver things to their house knowing that none of them enjoy going outside. She tells Kris that she does what she can to be helpful to them since they always seem so "easily forgotten". She seems to be one of the few townspeople they actually let inside sometimes.

When "the nobody" is given Tenna, "the nobody" actually begins letting Emma into the house more often to watch television with them, Napstablook and the irritable ghost (later Pink), whenever the workday is over.

Emma says the baking competition shows are her favorite, especially the holiday-themed ones, though she also enjoys cartoons and gameshows.

Not really sure of the specifics as to how exactly (perhaps a failed attempt to rescue Undyne that Mettaton made up as an excuse to finally get into the Dark World. I do think it would be Mettaton that connects the dots and opens the way in similar to how Pink found a way in), but Emma does end up visiting the Dark World, specifically TV World. However, since Tenna is now located in the Blook household, TV World has changed to reflect that (for example, it’s much more pink now with floral decorations, boomboxes and anime figurines).

She accidentally arrives there with "the nobody" (now fronting as Mettaton in TV World) who has taken the opportunity of possessing a robot body (not his EX one just yet) similar to Pink and her Mew Mew figure (though Mettaton doesn't have another personality to worry about as his robot body is an empty shell). While the two aren’t exactly sure how to return, they figure it's best to take their time assessing the situation, though Mettaton isn’t exactly eager to leave as he is THRIVING as Tenna’s new business partner.

Emma, as Mettaton’s friend, is doing her best to be supportive, but is conflicted because of Mettaton's family.

Her initial dynamic with Mettaton and Tenna is something of a third wheel. Since she and Mettaton arrived together and are both friends/the only Lightners, she is usually with him while in TV World. However, Mettaton immediately begins a business partnership with Tenna and becomes his co-host; now making Emma a reluctant member of the production team.

For a while (unspecified amount of time but probably less than a week), Mettaton and Tenna are LIVING IT UP! They are ECSTATIC to have each other and constantly putting on shows, feeding into each other in a loop of ratings, FUN™, and excitement.

While Emma is happy to see Mettaton’s drastic shift in mood, creative output and ‘hatched egg’ (remember, she’s known them mostly as their old ghost identity which they were clearly not happy with), she still feels a need to try to remind Mettaton that they initially came here to search for clues about the person who took Undyne and whether or not there is any information about getting into the bunker. She also makes a point to remind Mettaton that he has a family waiting for him back in the Light World.

Mettaton, of course, becomes annoyed at the idea of having to “go back” to before, drunk from success and living out his dream of being a star in the Dark World in a body he likes. Tenna notices the two seeming drearier, and while he’s happy that there is someone that finally wants to stay and work with him for potentially forever (ghosts are immortal), his experiences during Chapter 3 have also made him start to question some things; he especially takes note of the fact that Emma is trying to remind Mettaton that he has a family back home who would miss him.

Tenna decides to try talking to Emma one on one more, trying to understand her perspective in all this, considering she came WITH Mettaton into the Dark World. She finally admits that her friendship with the Ghost family means everything to her as they’re the ONLY friends she’s actually been able to maintain, having lost almost every other single person she’s tried to connect with over her life; whether through misunderstanding, her acting out during poor mental health episodes, or just losing touch; it’s clear that Emma is desperate for companionship and a family, even to the point of going along with Mettaton’s crazy plan. To her, the ghosts are the closest thing she has to a “family”.

She claims she’s “terrible for TV” since she never has any idea what people are actually thinking or what people actually want and that she’s unintentionally/accidentally burned more bridges than she can keep track of. She claims she isn’t good at making people happy or excited, just annoyed or tired; sometimes even scared. She also admits that she loves people like Tenna and Mettaton because they just seem to effortlessly bring so much hype and life to the party; she loves how good they are at putting on a fun show that makes everyone so happy.

After finally hearing her confide in him, Tenna becomes fixated on her, shocked to find out how much they have in common in terms of their struggles and anxieties. He likes Mettaton of course; Mettaton gave him a new home after all and loves performing just as much as Tenna does, but while Mettaton is fixated on becoming a huge star, getting a bit drunk off his own success (like a certain mailman once did), Emma is more concerned with trying to help him see some reason. This is something Tenna connects a bit more to and begins to seek out Emma’s company much more than before.

As the two bond, they find out how much they have in common besides their struggles, how sappy they are at heart, their happier memories of happier times, their fears of being outcast and abandoned… She says such nice things to him, such kind words, genuine ones... and oh no, they're into each other now I guess.

Mettaton, who has also been getting pretty "close" with Tenna notices this, and while not bothered, does see it as a chance to try and take the reins when it comes to the show; feeling a sudden need for control as he grapples with the complicated feelings of returning home and whether he even wants that or not.

Anyways things go a little silly crazy or something. Mettaton and Pink have a very similar arc of "no I don't wanna leave the dark world, I'm living out my fantasy here" type shit except Mettaton fights the idea of leaving way harder.

Also Spamton shows up because of the floppy disk Mettaton had in his home that he hoped would have the designs he worked on at the library, unwittingly taking Spamton with him. This also makes things complicated... ANYWAYS- here have some videos that explain it better: