The Sound Test is a somewhat hidden option, you can consider it a cheat in the original FE and it appears here. You can access and listen to every music and sound effect, if at the moment of continuing with a chapter (after completing it) you select "No" when asked to continue and then press:
Up, Down, Left, Right, Up, A.
Also, pressing START after the sound test screen allows you to enter a "test" mode where a battle is displayed with every possible weapon and class combination.
The Pegasus sisters (Palla, Catria and Est) can make a triangle attack; surround the enemy in a triangle-shape-like formation and then attack to make an automatic critical hit.
Stat increase on Manaketes
If you use a Promotion item with Bantu or Tiki, although it obviously won't work, you can gain permanent stats for them. The bonus obtained depends on the stone that Bantu or Tiki uses; You will gain the defense that normally get for using the stone, but permanently. The gain is maintained after chapters and can exceed the limit of 20 up to 99 (which will then turn around and return to zero, but still has the maximum defense in fights).
A side effect, however, is that the enemy will prefer to surround Tiki or Bantu rather than attack them... unless it is with magic since it is the only way to cause damage if they cannot with physical weapons.