Super Mario RPG, the original and the remake, is full of secrets, references to other video game franchises, and a whole lot more. Arguably the most interesting secret boss of the original game was Culex. He is not a Final Fantasy character, but he looks and feels like one and features Final Fantasy music and sound effects.
Culex appears in Super Mario RPG remake as he did in the original game, which is to say he is a pixelated, 2D creature. He also features the original throwback soundtrack and sound effects. You access him the same way, too – by buying fireworks and trading them with the little girl nearby in Moletown for a shiny stone. You then use that shiny stone in Monstro Town on the locked door.
However, upon defeat, Culex teases another encounter in the future, which is where things in the remake get interesting.
The first thing you need to do to get on this path is beat Super Mario RPG remake. Once you do that, head to Merrymore and stay the night in the fancy suite. During the night, Geno will notice something happening on Star Hill. Upon visiting Star Hill, you will find new pink stars in the third area that seem to come from bosses you previously defeated looking for rematches.
Full transparency: I am not sure in what order you need to defeat these bosses or if it matters. Mallow’s frog father will provide additional hints beyond the stars to help you figure out where to go. These bosses can be tough, and though I will provide some hints that helped me, much if it comes down to everyone being max level 30 and equipping the right items.
In Monstro Town, you must go back to the school and show the teacher how to pull off the Triple Moves. Much of this fight comes down to pulling off Action Commands.
In Marrymore, you must fight the cake again. I had luck putting the non-cake enemies to sleep to prevent them from lighting all the candles.
In Belome Temple, you must fight Belome a third time.
In the Sunken Ship, you need to head back to the Pirate Base to fight Johnny the shark in a one-on-one fight as Mario. I kept Bowser and Geno in my party to take advantage of their upgrades, but this fight really comes down to pulling off Action Commands almost exclusively. Defeating him gave me an Extra-Shiny Stone.
Booster is back in his tower and has a devastating train attack that will wipe out your party. I had luck ignoring everyone but Booster, getting Geno’s speed as high as possible with Zoom Shoes, and trying to get hits in before he could work on his train.
Finally, I tackled Punchinello again in Moleville who ended up being my most difficult fight. He has low HP, but a powerful shield that only lets you do one or two damage at a time. The best strategy I found was using Mario’s Lazy Shell and Bowser’s Drill Claw to hit his bomb compatriots so that they turn around and attack him for 80 damage a piece. The bombs who continue to face forward will attack you, however, and often knock out party members in one hit.
Equipping Peach with the Enduring Brooch, which prevents the holder from going down once per battle, was valuable in all of these fights.
Once you defeat all those bosses and acquire their various items and weapons, head back to Monstro Town and Culex’s door will have reappeared, meaning it’s time for the rematch. Use your Extra-Shiny Stone to enter. This time Culex, his soundtrack, and sound effects are as remade as every other element of the game.
Good luck! And let me know if you have any tips, because I am still working on defeating him.