In which this might be explained in an understandable way...
Ten Travellers
Two fillies burst into the Golden Oaks Library, before slamming it on the surprised looking royal guards stationed there.
"Princess Celestia! Princess Luna!" They shouted as they pushed passed several unicorn detectives.
The princesses look towards the eager fillies.
"I'm sorry you two, we still haven't found anything out about the disappearances yet" Celestia says in a letdown tone.
"But we have your majesties!" The first filly, a light grey, blond maned unicorn, says gleefully.
"What doth thou mean 'you have'"
"We think you know who's responsible!" the second, a light opal-grey unicorn with a purple mane, replies.
Everypony in the room looks in disbelief at them.
"Tootsie, if you please" the light grey one motions for her friend to start explaining.
"Right Dinky! First a whiteboard"
Dinky magics a whiteboard (as in a presentation white board, not a school room one, but it's still at least three times her size) into the room,"There you go done, you have the photos right?"
Tootsie opens her saddle bags and pulls out a stack of photos.
"Right here" she starts " Now, lets start with who's missing, we have..."
She sticks up the photos one above the other, as she reads out the names,
"Princess Twilight Sparkle, Miss Rarity, Miss Fluttershy, Rainbow Dash, Applejack, Pinkie Pie"
One of the Detectives butts in,
"We already know this"
Another punches him on the arm tells him to shush, Tootsie goes on, but puts every two next to each other,
"Momma Lyra, Mommy BonBon, Dinky's mom Ditzy 'Derpy Hooves' Doo, Zecora, The Doctor, Miss Cheerilee, Ovtavia and Vinyl 'DJ Pon-3' Scratch. Dinky" she finishes swapping magical claim of the photos with Dinky,
"Right! Now we've noticed a few new ponies who have been here since the first day everypony went missing. They've also been going around in cloaks, all mysterious like. We did a bit of sneaking peaking and have discover where they've been camping out and managed to snap so pics of them, aaaand found out their names"
"Wait a minute, what new ponies?" The local detective asks.
"They seem to be avoiding you, all of you" Dinky replies
"But they didn't avoid you?" Another voice says
"Hey, we're just little fillies playing, what need is their to avoid us?" Tootsie says fringing innocence.
"Anyway" Dinky continues"We have photos and names, meet..."
She puts up a picture of an earth pony colt across from Twilight Sparkle, and who looks a lot like her, only darker and with a shorter mane. She leave enough room for another photo,
"Dusk Shine, We managed to get a snap of his Cutie Mark too"
She sticks it up and everypony gasps,
"T-t-that's Princess Sparkles cutie mark!"
"And he's not all, meet the whole team, Elusive. Butterscotch, Spectrum, App..."
"Is that the right photo?"
Both fillies look up at the photo, it's a zebra mare, her mane is long, it's style reminiscent of Fluttershy, in the colours of Rainbow Dash's but reversed, and unlike the others her cutie mark isn't the same as Rainbow Dash's.
The fillies look back to the princess and reply,
"Yes"
Dinky elaborates further,
"We heard them say she was the loyal one, and the mane colour makes it easier to figure out"
"I see" Celestia says nodding "You may continue now"
"Thank you princess. Now than, ah yes, Apple Jack, two words, and the final of the recognisable ones, Bubble Berry"
"Final recognisable one?"
"Yep. The rest don't look like any of the missing ponies"
"Then how do you know they're responsible?"
"'Cause they've been hanging around being familiar with them"
"Tootsie be nice"
"Sorry Dink"
"Anyway"
Next to the pictures of Lyra and BonBon she puts a picture of a pale honey yellow pegasus with honey orange mane, her cutiemark is of a honey dip 'healing' cracked love heart.
"Meet Honey Dip, Element of Love"
"Element of Love!? Now your just making things up, their are only six elements and love's not one of them, even if it was, wouldn't Princess Cadence hold it?"
"Do not be so rude Detective, We hath heard of miss Tootsie mothers love and, We quote our niece when we say this, 'there is no greater force of love in this world'"
"It's true, that was word for word Cadence's comment from when we visited Twilight on birthday last year. But still, that doesn't give reason to why you say there is an extra Element"
"Four actually, we think that we don't have them because their shared, it's slightly awkward and would be difficult to beat baddies if you have to share a necklace" Tootsie explains
"Well maybe not awkward for you moms..."
"Dinky, please"
"Sorry. Anyway"
Next to the pictures of Derpy and Zecora she puts up photo of the head of a burnt orange unicorn with a mauve mane, however she also puts another of an identically colour winged back and tail.
"Hmm, that explains the disturbances we've felt sister"
"What is this colt's name miss Dinky?"
"Exile, at least that's what they call him. We think he's the Element of Hope"
Next, Dinky puts up a picture of a dark indigo earth mare with a black mane and a cutie mark identical to Celestia's only completely black.
"This is Solar Shadow, The Element of Trust, she seems a lot like Miss Cheerilee"
Her picture is next to ones of The Doctor and Miss Ceerilee.
"And finally, the Element of Song"
She puts up a picture of a griffin, he has light reddish/brown feathers, similar coloured fur, and strange grey eyes.
"He sounds funny. We're not sure what his name is through they all just address him by his element"
"Wait? A griffin beari..."
"The Elements of Harmony are not equine specific Detective, stop being so close minded"
"Thanks for the defence love" a new voice rings out.
The owner is quickly located, it's the same griffin from the photo, and he's standing with the first colt, Dusk Shine, as well as the alicorn Exile and the pegasus Honey Dip.
Tootsie calls to them,
"Hey, it's you! Where's our momma's! Oh, and the other elements?"
"Indeed, and how did pass our guards?"
"Walking, and Dusky can explain where everyone is"
He stepped to the side as Dusk steps forward,
"As these two have found out, we are, technically, responsible for the disappearance of your EoH, when we came to this universe, we accidentally sent our counterparts where we were. Now, don't worry no harm will befall them while they're there"
"So how do you plan on getting them back." Celestia expression is unreadable, but her voice says that it was a statement, not a question.
Luna realises something.
"What has happened to the detectives!?"
Dinky and Tootsie, gasp at the frozen forms of detectives, Celestia turns and glares at the intruders.
"The same thing that's happened to the rest of Ponyville. This reality trying to correct itself, but to do so it needs to weed through everything else, stoping what is right as not to harm it. Your majesties are to powerful for it to decided, we obviously aren't right, and those two are anchored to those we swapped"
...
...
...
The griffin leans forward and whispers to Dusk,
"Just cast it. We won't stay so no harm done"
"What do you mean you won't stay What spell are you casting?"
Dusk rises a forehoof and points it towards Honey, she starts to glow, then he raises the other towards Tootsie, who also starts glowing.
"Stop! What are you doing!?" Celestia demands.
Exile raises a hoof to his lips and shushing her.
There is a bright light, when it dims, the intruders are gone, and so are Tootsie and Dinky, the detectives start moving.
Celestia and Luna look shock. Then both rush to the door, ripping it open ,they order their guards to start searching for the alternate Elements and the missing foals.
