From: Anagram | #050
Spoilers
But partway through the game, Cait Sith lets the temple destroy him while he's still on top of the doll, and then shows up again and is all "No big deal."
It's a different Cait Sith.
The one in Advent Children is arguably yet ANOTHER Cait Sith since it has a Scottish accent, as opposed to the Southern dialect FFVII's Cait Sith No. 2 had.
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"Stay with me until the end. Please."
"Not until the end. Always."