This is the part where we see Tirek return in Thomas' Place as a Prime.
[Meanwhile somewhere else]
Tirek: [breaks free from his prison] Finally! I'm free! Now I shall need to get a new army, and I know just where to get one!
[looks to the mountains]
Tirek: Megatrain's army will be mine! [echos]
[in the castle Princess Celestia hears the echo]
Princess Celestia: Tirek is free!
Princess Luna: What is it?
Princess Celestia: Tirek, is back!
Princess Luna we must tell the others immediately!