Mimi insists that Roy and Farah get started on conceiving her right now. At gunpoint.
Several people come back from many different timelines, each one where Roy choses a different member of his Unwanted Harem.
Downplayed: "Hey Roy, Farah." "Who are you?" "Oh, just a passerby who just happened to know both your names. Probably since I'm your daughter from the future. Anyway, have a nice day you two, bye." "Bye."
Justified: This is part of a Stable Time Loop. Mimi had to come back because Roy and Farah already met her in their past.
Parent from the Past. A person goes forward in time to meet their offspring.
Parent from the Future. Roy is from the future and travels back in time to visit Mimi, his daughter with present-time-dweller Farrah.
Mimi is actually an agent of Emperor Evulz who has been sent back to ensure that Roy doesn't hook up with Sharon and produce Jon.
Farah points out that it is impossible to be their kid after they both wound up sterilized from radiation exposure.
Jon shows up from the future himself to prevent Mimi's meddling with his past.
Mimi correctly points out it doesn't matter in the future.
Parodied: Mimi is actually an actress hired by Roy and Farah's friends to try and force the pair to admit how much they really like each other.
Zig Zagged: Mimi is the daughter of Roy and Farah, while Jon is the son of Roy and Sharon. Mimi is an agent of Emeror Evulz, sent back to prevent Jon's birth, but Jon is an agent of another evil villain, and he's been sent back to prevent Mimi's birth, as the two villains have contrasting opinions on who is the Chosen One. After a confrontation, Roy, Sharon, and Farah agree to let Mimi and Jon both exist, as they don't know who the Chosen One is either. In the future, because of this, Mimi and Jon have a child, and that child becomes the realChosen One... Roy.
Averted: Although time travel is possible in the setting, no one ever uses it to visit their relatives.
Enforced: "We want to show that Roy and Farah are the Official Couple, and it's a fantasy show, so how about their future daughter shows up?"
Lampshaded: "I've been working on my relationship with Roy for months now, and we're finally getting along okay. Then you come back into town and five minutes later, your kid from the future shows up! How is that kind of validation fair?"
Invoked: Mimi builds or buys a time machine specifically for this purpose.
Discussed: "Y'know, that new girl looks like Roy, but with Farah's coloring. Do you suppose she's their daughter from the future?"
Conversed: "There's a new little girl in the previews that looks kind of like Farah and hugging Roy. And the title is 'A Surprise From Tomorrow'. I call Kid from the Future."
Mimi's stay in the past alters it in little, unforeseen ways; unfortunately, this eventually spreads to affect the period of conception — just enough that they don't concieve her, wiping Mimi out of existence. The shock of having their future child disappear further rocks their relationship, as Farah and Roy accuse each other of doing something horribly wrong. Ultimately, they break up, dooming Mimi to nonexistence.
Farah and Roy really don't like each other, but now feel like they have to get together Because Destiny Says So. Pent-up resentment, frustration and anger have massive, negative repercussions on their relationship. But Mimi never said they were happy together, only that they were her parents. Indeed, she thought that by coming back she could prevent their family from becoming so dysfunctional, but instead has created a Stable Time Loop that ensures their future misery.
Mimi is squicked out by seeing her parents her age in a relationship. This causes enough emotional problems for her to fail at whatever the reason was she came back.
But then Mimi's own daughter appears and convinces her that she turned out alright in the end.
From the first entry in "Deconstructed," Mimi's actions caused her to never be conceived. But because she is outside of the proper flow of time she doesn't disappear. She has to remain in the present as there is no home for her in the future, But one of her former parents decide to adopt her as a sister.
Played For Laughs: Roy and Farah frequently insist that they aren't dating and don't even like each other, and already had trouble convincing their friends... and now there's this kid running around claiming to be their child from the future? AAAUUGHH!
See the first entry for "Deconstructed," only Mimi knows that her appearance in the past will erase herself from the timeline. She goes through with it anyway, because something horrible happened in her timeline, and she wants to spare Roy and Farah from that fate, even if it means they don't end up together and have her.