There's a number of monsters late game that have completely different battle scripts.. for those that are interested.. here's a number of them worth looking at.
Blue Dragon
Battle Script 0x79
If Casted on by Character with Lightning
Note: I'll explain it later, but this is wrong already.
Counter Script 0x7A
If Self has Charm
Target 敵味方
Fight
Always
Fight
(End of Turn)
Cast Blizzard ($9C)
(End of Turn)
Fight
(End of Turn)
Fight
(End of Turn)
Cast Blizzard ($9C)
Note: The Charm script will not execute since the monster has natural resistance to Charm (regardless of the Boss Bit).
I'd swear the scripts are actually swapped, but for the sake of argument... and the counter script resembles something a little different.
If attacked by a Fire elemental magic attack, counter with Blizzard. (edit)
In FF4ET, this script is radically different...
Battle Script 0x79
If Casted on by Character with Lightning
Note: It's still wrong, but I'll explain that later too.
Counter Script 0x7A
If Self has Charm
Target 敵味方
Fight
Always
Fight
(End of Turn)
Cast Lt.Flash ($98)
The Charm script will obviously never execute for the previously mentioned reason.
This is a radical departure from the original monster, since instead of being a cold elemental attacker (with freaking insane absorb properties), it is now a Lightning elemental monster that is extremely weak against both Fire+Ice (but not Holy for some reason).
The counter script is more like this:
If attacked by any magic (including non-damaging magic, but summons are not included here in this counter), counter with Lit-3/Bolt-3.
As you can see, they changed one really vicious monster into a relatively tame one...
Here's another monster... the Tricker/Rilmarder/Lil' Murderer:
In FF2/4, it's really simple...
Battle Script 0xE8:
Always
( $2 $0 $0 $2 )
Target キャラクタ全員
Cast Lit-3
Always
Target Enemies in Current Group
Cast Peep
Counter Script 0xE9:
If Casted on by Character with Lightning
Battle Message $AF
Battle Message $B2
Target Enemies in Current Group
Cast Fast
$F3 to $F8 - $82
It's pretty straight forward since the common behavior is known.
In FF4ET.. it looks more like this... (using Dragonbreathren's FF4ET patch)
Battle script 0xE8:
Always
( $2 $0 $0 $2 )
Target キャラクタ全員
Cast ire3
Always
Target Enemies in Current Group
Cast can
Counter script 0xE9:
If Casted on by Character with Fire
Battle Message $AF
Battle Message $B2
Target キャラクタ全員
Cast ire3
$F3 to $F8 - $82
If Casted on by Character
Cast Wisper ($70)
So, on basic analysis alone, this monster mainly acts the same, but it does react to Fire instead and everything else is countered. It's not that dramatic, but these are the kinds of subtle changes made (mainly the Lunar Subterrane bosses have the most dramatic changes). So, for those people who say FF4ET is the same as FF2, they are really really wrong.