Post Credit Save Menu

[C-Dude]

These are the event bits set and cleared by the ending, as far as I could find.

Code:

CA094D: {D6-9A}               Set event bit $1E80($39A) [$1E93, bit 2] Shows some NPC
...
CA0E24: {D6-9E}               Set event bit $1E80($39E) [$1E93, bit 6]
CA0E26: {D7-F5}               Clear event bit $1E80($3F5) [$1E9E, bit 5] Hide some NPC
...
CA1389: {D4-E3}               Set event bit $1E80($2E3) [$1E9C, bit 3]  Shadow's covered up in shops?
...
   CA1395: {D4-C0}               Set event bit $1E80($2C0) [$1E98, bit 0] Cinematic effect (gets cleared later)
CA1397: {D6-A0}               Set event bit $1E80($3A0) [$1E94, bit 0] Show some NPC
...
CA149C: {D2-C6}               Set event bit $1E80($1C6) [$1E98, bit 6] Shows portrait in epilogue (Set multiple times)
...
CA26B9: {D7-A0}               Clear event bit $1E80($3A0) [$1E94, bit 0] Hide some NPC
...
CA26D4: {D5-F3}               Clear event bit $1E80($2F3) [$1E9E, bit 3] Make Shadow unavailable (seems designed to mark that he died in the ending.  Why?)
...
CA2921: {D6-FE}               Set event bit $1E80($3FE) [$1E9F, bit 6] Show some NPC (set and cleared several times, may not be cleared at end)
...
CA29EB: {D6-9C}               Set event bit $1E80($39C) [$1E93, bit 4] Show some NPC
...
CA30D4: {D6-9D}               Set event bit $1E80($39D) [$1E93, bit 5] Show some NPC
...
CA3645: {D6-9F}               Set event bit $1E80($39F) [$1E93, bit 7] Show some NPC
...
CA36EA: {BA-20}               Play ending cinematic $20
CA36EC: {BB}                  {BB}
CA36ED: {FE}                  Return  [END OF GAME]

There isn't an event bit that skips the Kefka fight, but if you don't reverse some of these bit markings before calling a save, things may not work the second time around (missing NPCs, event freezes, etc.). You'd also need to plop the player on the position of an existing save point (perhaps the classroom) before you prompt for a save, since saving records your position and it probably wouldn't be valid after end credits.
It's easy enough to clear event bits that were set during the ending, but it's not so easy to determine which cleared bits have to be turned back on.