Buggy Rippler
Strago's Lore ability Rippler has the effect of exchanging the current status of the caster with that of the target. It was meant to exchange common statuses, such as Blind, Slow, or Protect. However, due to a bug, Rippler interacts with all statuses – even special ones which are not named or visible. These include Magitek, Critical, Trance or Interceptor Guard. Using the ability can therefore have many unexpected, strange effects. For example, characters affected by Rippler can use their Desperation Attack even when not low on HP (only the Critical status is transferred, while HP remains unchanged) and you can even permanently lose Interceptor (the dog companion) if an enemy casts Rippler on Shadow! This bug has been fixed in the iOS/Android/Steam version.
Another bug causes Rippler to seemingly miss its target, while in reality it does not. This was fixed in FFVI Advance. But then a new feature has appeared, causing characters and enemies who are immune to the Imp status to also be immune to Rippler. It may possibly be a bug as well.
The video below (uploaded by Smythejameson) shows one of the effects of the bug in action – Strago (confused) casts Rippler on Terra in Trance status, eventually resulting in two Trance Terras on the battlefield.
Info source: https://finalfantasy.fandom.com/wiki/Rippler_bug