I think players are trying to play joke on me, I'm thinking of turning it back.

[Drakoun]

Well, first of all i'd suggest that if you haven't seen the show yet, you should give it a shot at least.
Second i guess the easiest way of resolving this ... problem? is by simply asking your players if they really want to play in a MLP setting and if yes, to what extend. I, for example, would love to play a game set in Equestria, even if it were a little darker.
If they really like the show it might not be a good idea to twist the universe to much (dunno how much humorous your players are...)
Lastly i'd suggest that you really should just watch the show :P
if you aren't patient enough to watch at least the first few, start off with season 2 ep 3: "lesson zero"

[Acanous]

Really, what it seems the players are expecting here are MLP-based characters in a D&D World. They know you don't watch the show, so they expect a standard D&D adventure out of you, not a MLP setting.

Imagine the MLP cast playing a game of D&D in their free time. Your game is that game.

So really, don't change your world. Don't worry about the poniness. Just run a game of D&D, and let your players worry about the roleplay.

Trolling them back on purpose will deprive you of your DM hat.

[Malachei]

Or should I just laugh it up, and say be serious?

This. Unless you're convinced your players (and you) will actually have fun. If you have enough spare time at your hands, you might want to give it a try. But before you delve into sources and create a setting and an adventure just because your players have played an April Fool's Day thing on you, you could speak to one of them and ask him/her if the group really wants to play ponies. It's not like having a one-shot is bad, and perhaps this really caters to your players' interests, and who knows, you might see a years-long pony campaign, but still: It would not be my cup of tea.

[Leon]

Let them play what characters they want. In Ravenloft.

[Acanous]

Let them play what characters they want. In Ravenloft.

This is a perfectly acceptable solution.

[Malachei]

Let them play what characters they want. In Ravenloft.

Or in Tomb of Horrors.

[Asheram]

So I sent out an e-mail to saying I might run a game but wasn't sure what setting. Then I got a bunch e-mail from the players stating they want to make characters like a ranger who owns an apple farm with her brother and baby sister who happens to named Ashley "Apple" Jack. Another making a wizard who trained under the wizard ruler and had a nicknamed "Twlight" or "Sparkle". The list goes on such as "Pinkie" or "Pie" as a bard or a Tomboy Monk who dyed her hair and named Rainbow Dash.

While I have never seen MLP how should I go about making a scenario for the campaign. I only know the basics of the shows like the character's name and basic summary of their personalities. Or should I just laugh it up, and say be serious?

Naw, but in all seriousness, I suggest you play it straight and make it a one-shot adventure in Equestria... Spiced up D&D style ofcourse.

[Telonius]

Would these gamers be old enough to remember the 80s cartoons? You could set it up as a plot by the older ponies (maybe the one with the jewel-eyes?) to re-assert power. Bonus plot point: iirc, there was a pony named Rainbow Dash in the original. Is the monk a sleeper agent?

Ready-made villains: a trio of bumbling witches, a bunch of evil bee-folk...

[BlueEyes]

Bonus plot point: iirc, there was a pony named Rainbow Dash in the original. Is the monk a sleeper agent?

There is a Rainbow Dash in the new version too. She's one of the mane six characters.

[Telonius]

There is a Rainbow Dash in the new version too. She's one of the mane six characters.

That's the point - plot hook being that the "Rainbow Dash" monk might know something about their enemies, or even be working for them.

[Keld Denar]

The Tentacalli crime family? But they're in disarray after Chresti and Mimic stole their Magic Missile...

I approve of your reference! Well played sir! I think it was Presti, though...

[The Glyphstone]

I approve of your reference! Well played sir! I think it was Presti, though...

You are correct, I am ashamed.

[CTrees]

Or in Tomb of Horrors.

My Little Tomb of Horrors: Friendship is Trapped was my first thought, too.

[Hiro Protagonest]

I approve of your reference! Well played sir! I think it was Presti, though...

Actually, I think it was Prestige Perkins.

...

Practiced practitioner of practical Prestidigitation.

[Akisa]

Well I'm off to gm ponyfinder. I took everyone's advise and watch the show, I seen it from Nightmare moon to some doploganer pretending to be a princess for a wedding to feed on love.

[Drakoun]

weeell, does that mean you like the show now? (you watched all 52 episodes Oo?)
Anyways, please tell us how it went with your players.
would love to read more about your game and if you could pull it off successively. (or rather how you actually play 'ponyfinder' )

[moritheil]

Going into more detail, the ruler of this land is a power mad Mage (wizard, cleric, whatever) who demands the adoration of all. Draw inspiration from Lord of the Rings my friend, "And now at last it comes. You will give me the Ring freely! In place of the Dark Lord you will set up a Queen. And I shall not be dark, but beautiful and terrible as the Morning and the Night! Fair as the Sea and the Sun and the Snow upon the Mountain! Dreadful as the Storm and the Lightning! Stronger than the foundations of the earth. All shall love me and despair!"

Waker, you are the man.

[Waker]

I love that part of the book/movie. Something doesn't have to be covered in horns or dripping ichor in order to be scary, comparing herself to sheer elemental power was enough for me. My absolute favorite line in the entire series though is "All shall love me and despair!"

[Akisa]

It turned out they were joking and weren't expecting to play those characters. So I managed to convince the group to play in the world using their real characters, but tweaked them to be ponies from Pony Finder. The session was ok, I wasn't prepared as I would like as I spent most of the time doing research of the show.

But I played it off as Celestia is manipulative in her goals and is sort of a tyrant. Has agents in other kingdoms to subvert their control and in the past to gain control like she did to Pegasopolis, Unicornia and Earth. Celestia is trying to conqueror through manipulative take control the country of Trotterlot. The PC managed to find that local mayor and police chief a city was replaced by some Celestia's minion using disguise spells. Among the plot they discovered part of the ritual summoning of Windigoes (although they weren't named as such) and with plans of starting of infighting so they could be fed.

I mostly had to improvise the last portion of the scenario, as I needed a plan how would Celestia gain control of a nation, aside for impersonation. The group wants to continue to see where it leads.