At some point in the BtVS or AtS canon, one of the characters ends up going through some kind of portal (or otherwise ends up thrown into another dimension) and wakes up on the other side to find him/herself de-aged and stuck on a very strange desert island. They're soon taken in by the characters from LOST and have to deal with the dangers of the island... and the fact that everyone thinks he/she/they are too little to take care of themselves.

Options:
The de-aged character can be de-aged both physically and mentally, or just physically, such that they look like a child, but sti...

Faith always thought her father must have been a real piece of work, but she never imagined that he might be Mossad. At some point during Faith's teen years, Ziva discovers that Ari wasn't the only result of her father's indiscretions. She finds Faith and takes her in, saving her from the self-destructive path she's heading down.

Requirements:
Ziva dealing with having another sibling, when Ari and Tali are gone.

Faith dealing with having someone who cares about her...and lashing out when she's scared it might go away.

The NCIS team making Faith part of their fa...

Crossover with the CW show "Life Unexpected."

Sixteen-year-old Lux has survived the foster care system, reunited with her birth parents, and is slowly learning how to be a daughter (while 32 year old Cate and Baze learn to be parents), but the drama up until this point is nothing compared to what happens when her new social worker turns out to be a Watcher undercover, and the whole blended family is drawn into supernatural drama.

Options:
Lux can be a slayer/potential slayer OR it can be revealed that Cate USED to be a potential, and Lux's birth was part of some mystical ...

When Buffy discovers that Hank Summers wasn't her father, she goes in search of her real father, but instead of finding him, she discovers instead that she's not the only daughter he hasn't officially claimed. In other words, Buffy has 3-5 sisters from other fandoms, who may or may not know of their true parentage, but definitely do not know about the rest of the siblings. In a quest to discover her roots, Buffy unites her sisters, discovering a lot of adventure and a few conspiracies along the way.

Requirements:
+The fic MUST be a multiple cross

+The sisters must physi...

After Buffy dives into the portal for The Gift, the monks' spell begins to unwind. Dawn manages to keep her human form, but the unwinding spell gives her more access to her key powers. Meanwhile, the memory portion of the spell is completely undone, and suddenly, nobody in Sunnydale remembers Dawn at all, and in the wake of Buffy's death, they aren't exactly in the mood to listen and end up chasing Dawn, who they believe is some kind of sick practical joker and/or demon, out of town.

Enter the crossover- your choice as to fandom. Dawn doesn't have a home, money, friends...she has N...

When Wash dies, he somehow ends up reincarnated as a small child in the Buffyverse. One or more of the Scoobies become his family, and little Wash enjoys life on Earth That Was... until visions of his past- and the future- come back to haunt him.

Options:
The Buffyverse can either be an alternate universe from the Firefly verse, or it can be its past. Your choice.

Requirements:
Xander and Little Wash hanging out.

Plastic dinosaurs, of course!

Wash flirting with a little girl, and remembering Zoe.

Wash making subconscious comparisons be...

Familiar set-up, different fandom. One of the BtVS or AtS canon characters is transported to Middle Earth, but crossing dimensions causes a magical backlash, and as a result, they come out the other end of the portal as a child. From here, there are several options.

Option 1: Set the fic years before the Fellowship, when Aragorn is growing up among the elves as Estel, and make the BtVS end up among the elves as well, as a foster brother or sister to Aragorn and company. Alternatively, you could have him/her adopted by another major player (ie grow up as a sibling to Eowyn, or adopt...

Crossover with Firefly. Dawn's keyness somehow causes the two girls to switch bodies. Now Dawn is in River's body, 500 years in the future, and River is in Dawn's body, in Sunnydale.

Requirements:

Show the parallels between Dawn's life and River's (ie both have overprotective older siblings who would die/give up everything to save them, both have their crazy moments, both aren't quite part of the crew/Scooby Gang, both have had people mess with their minds/memories).

Have Dawn try to explain things to the crew of Serenity, only have the crew think that River is j...

Crossover with SG-1.

When Dawn starts bleeding on the tower during The Gift, her keyness connects her to the Stargate in a nearby dimension, and- rather than either Buffy or Dawn jumping- Dawn is sucked into that dimension, and into the SGC, through the gate. Eventually, Dawn is spat out into the SGC, unconscious and still bleeding.

Requirements:
Dawn's youth must get Jack's protective side up

Dawn meeting Cassie

Dawn partaking of the teenage angst

Dawn staying (temporarily or permanently) with a canon character (bonus points if she lives wit...

Crossover with Stargate SG-1.

A twist on all of those "Buffy is Jack's daughter" fics. Buffy is Jack's biological daughter- either adopted by Hank and Joyce, or a Joyce/Jack love child. In any case, Jack doesn't discover her existence until she dies, leaving the good Colonel to mourn a second child. Months later, when the Scoobies bring Buffy back, she isn't alone. O'Neill's son, Charlie, is resurrected as well.

Options:
+You can do this fic with or without Dawn. Bonus points, though, if Dawn is around and ends up in Jack's custody during Buffy's death and resurrec...

Inspired by Jinni's Parent Trap challenge.

At some point in time, a person from the Buffyverse and a person from Firefly have a relationship and end up having twins. They reach a rocky point in their relationship, and whichever character has crossed worlds/times ends up going back to his/her own time, and bringing one of the babies with them. When the kids get invited to a special summer camp, no one realizes that it exissts in a dimension that isn't tied to time, and the kiddos meet up and decide to switch places.

Requirements:
One of the children must be raised with t...

Futurefic, crossover with Supernatural.

The Summers sisters marry the Winchester brothers (how these pairings happen, and which combination you use is up to you), and Dawn and Buffy end up pregnant at the same time. A few years later, Dawn, Buffy, Sam, and Dean have to deal with two kids who have huge destinies- and genetic predispositions for trouble.

Options:
This can be either a kidfic (the children are between the ages of 4-7ish) or a teenfic (the kids are teenagers).
The pairings can be either Dawn/Sam and Dean/Buffy, or Dean/Dawn and Sam/Buffy
I'd prefer bo...

When Giles and Joyce have sex during Band Candy, a child is conceived, but the Powers that Be take the child to another dimension to be born and grow up. When the Buffyverse and this other dimension collide, the Giles/Joyce love child finds out his/her heritage.

Options:
You can have time running differently in the two dimensions, and as a result, Buffy's younger sib's age does not have to match up with the age the child would have been had it been born in her dimension. The child can be older than Buffy, younger, or the same age- all are fair game.

You can bring Buffy ...

Crossover with Grey's Anatomy. Warning: requires the mangling of time-lines.

When Buffy died in season five, she was immediately reborn- to a teenage Izzy Stevens. Izzy gave her up for adoption, and went on to med school. Now, six to ten years later, Buffy's slayer powers have returned, and demons kill her adoptive parents. Suddenly, Izzy's a mom to a mini-slayer, and mini-Buffy is dealing with random memories of her former life.

Requirements:
Some subset of the Scoobies must come to meet/protect mini-Buffy.
Buffy living with Meredith, George, and Izzy
Chri...

Crossover with Firefly- same tune, different show.

At some point in the BtVS canon (either directly post-Chosen, or set at a specific point in seasons 1-7), one or more BtVS characters is pulled through a time portal- 500 years in the future. They land on Serenity. The catch? The character(s) has traveled forward in time, but somehow, the aging process has been reversed, and they land on Serenity as a small child.

Requirements:
At least one, and no more than four Scoobies are sucked into the time portal.

The scooby in question must be a child both physically a...