Here is how Forge's experiment goes wrong, Nighlock and Nur go to rescue the missing X-Men, and the Main Titles goes in X-Men in Equestria.
(the Future begins playing)
(We see Forge working on an experiment)
Forge:(to himself) Almost done and there. Finally, my world transport machine is complete. Now we can travel anywhere in the universe. Just need to test it.
(he picks up a phone and throws it in)
(when the phone doesn't come back, Forge takes it as a good sign)
Forge: Yes, I did it. The machine works!
(just then, the portal started malfunctioning, pulling everything in)
Forge: Me and my big mouth.(goes to shut it off)
(before he could, a piece of metal hit him on the head and knocked him out)
(we see some of the X-Men get sucked in)
Nighlock: Forge, what the heck have you done?!
Forge: I thought it worked! I'm sorry!
Apocalypse:(teleports into the room) The only way to stop this, is to go in after them! But that requires a major sacrifice!
Nighlock: I know. We have to shut down the portal from the inside.
Forge: But how will you two get back?
Nighlock: Hey, we're X-Men. We'll figure it out.(to Nur) You ready?
Apocalypse: Yes.
(they jump into the portal while the Main Titles play)
(X-Men in Equestria appears on the screen)
(screen turns black)