They caught me.
I tried to escape them as long as I could. Almost got away, got shot with some kind of dart.
Haven't heard from Pinkie in a while, so it's just me now.
I swear, being locked in whatever room this is will make me go insane eventually. There's no colour, no change to the scenery, just a blank, white room.
Wasn't able to eat for a while, thought of attacking the next thing to come in here, I was so hungry. Thankfully, the next time someone came, it was with some form of food. Hated the taste, but it stopped the hunger pangs.
I'm treated like some common animal, I swear. Last orange-suited person who came here actually tried to pet me. I didn't trust it, so I kinda backed up real far away.
He looked disappointed, honestly. Felt a bit bad, wanted to let him. They took him out before I changed my mind.
I hate it here, I really do... Oh mare, I want sis to come back...
Well, Mena, guess you're an SCP for now until Twilight can get you and Pinkie back.
Sadly, there's not much in the way of advice I can give. Don't bother getting attached to the orange-suited people, they're D-Class and get switched out every month. Like Avendrial said, you're likely get better treatment if you show you're sentient, so long as you cooperate with them. DO NOT tell them about Twilight, however. Your return to Equestria would likely constitute as a Containment Breach in their minds, and that is something they will prevent at any cost.
... that being said, if they try to stop you when the time comes, the best course of action would be to point out that you have no intention to return or become a threat to them or humanity as a whole. On the other hand, your status (well, Pinkie's status) as a prominent hero and VIP in Equestria means your return there would be highly desirable. Something they'd likely be willing to fight for. Roughly 1/3 of Equestrians possess some sort of reality-warping abilities (what you would call magic), with Twilight in particular being among the strongest of them. Celestia's control of the Sun and Luna's control of the moon, if it can be applied to this world, could easily cause an XK-Class End-Of-The-World Scenario, and Discord in particular has reality warping powers that only SCP-343 'God', and SCP-239 'The Witch Child' could hope to match. As the primary goal of the SCP Foundation as a whole is the protection and preservation of humanity, allowing your return and avoiding an inter-dimensional war is the only logical path for them to take.