--- a/net/minecraft/server/Bootstrap.java
+++ b/net/minecraft/server/Bootstrap.java
@@ -43,6 +_,7 @@
         if (!isBootstrapped) {
             isBootstrapped = true;
             Instant instant = Instant.now();
+            io.papermc.paper.plugin.entrypoint.LaunchEntryPointHandler.enterBootstrappers(); // Paper - Entrypoint for bootstrapping
             if (BuiltInRegistries.REGISTRY.keySet().isEmpty()) {
                 throw new IllegalStateException("Unable to load registries");
             } else {
@@ -54,11 +_,80 @@
                     EntitySelectorOptions.bootStrap();
                     DispenseItemBehavior.bootStrap();
                     CauldronInteraction.bootStrap();
-                    BuiltInRegistries.bootStrap();
+                    // Paper start
+                    BuiltInRegistries.bootStrap(() -> {
+                        io.papermc.paper.world.worldgen.OptionallyFlatBedrockConditionSource.bootstrap(); // Paper - Flat bedrock generator settings
+                    });
+                    // Paper end
                     CreativeModeTabs.validate();
                     wrapStreams();
                     bootstrapDuration.set(Duration.between(instant, Instant.now()).toMillis());
                 }
+                // CraftBukkit start
+                // TODO Check what of this is needed, maybe report it to Mojira. if deemed relevant, move to the respective classes
+                //  Used in CraftLegacy
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1008, "{Name:'minecraft:oak_sign',Properties:{rotation:'0'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'0'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1009, "{Name:'minecraft:oak_sign',Properties:{rotation:'1'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'1'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1010, "{Name:'minecraft:oak_sign',Properties:{rotation:'2'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'2'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1011, "{Name:'minecraft:oak_sign',Properties:{rotation:'3'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'3'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1012, "{Name:'minecraft:oak_sign',Properties:{rotation:'4'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'4'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1013, "{Name:'minecraft:oak_sign',Properties:{rotation:'5'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'5'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1014, "{Name:'minecraft:oak_sign',Properties:{rotation:'6'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'6'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1015, "{Name:'minecraft:oak_sign',Properties:{rotation:'7'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'7'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1016, "{Name:'minecraft:oak_sign',Properties:{rotation:'8'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'8'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1017, "{Name:'minecraft:oak_sign',Properties:{rotation:'9'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'9'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1018, "{Name:'minecraft:oak_sign',Properties:{rotation:'10'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'10'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1019, "{Name:'minecraft:oak_sign',Properties:{rotation:'11'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'11'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1020, "{Name:'minecraft:oak_sign',Properties:{rotation:'12'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'12'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1021, "{Name:'minecraft:oak_sign',Properties:{rotation:'13'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'13'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1022, "{Name:'minecraft:oak_sign',Properties:{rotation:'14'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'14'}}");
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1023, "{Name:'minecraft:oak_sign',Properties:{rotation:'15'}}", "{Name:'minecraft:standing_sign',Properties:{rotation:'15'}}");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(323, "minecraft:oak_sign");
+
+                net.minecraft.util.datafix.fixes.BlockStateData.register(1440, "{Name:'minecraft:portal',Properties:{axis:'x'}}", "{Name:'minecraft:portal',Properties:{axis:'x'}}");
+
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(409, "minecraft:prismarine_shard");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(410, "minecraft:prismarine_crystals");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(411, "minecraft:rabbit");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(412, "minecraft:cooked_rabbit");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(413, "minecraft:rabbit_stew");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(414, "minecraft:rabbit_foot");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(415, "minecraft:rabbit_hide");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(416, "minecraft:armor_stand");
+
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(423, "minecraft:mutton");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(424, "minecraft:cooked_mutton");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(425, "minecraft:banner");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(426, "minecraft:end_crystal");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(427, "minecraft:spruce_door");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(428, "minecraft:birch_door");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(429, "minecraft:jungle_door");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(430, "minecraft:acacia_door");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(431, "minecraft:dark_oak_door");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(432, "minecraft:chorus_fruit");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(433, "minecraft:chorus_fruit_popped");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(434, "minecraft:beetroot");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(435, "minecraft:beetroot_seeds");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(436, "minecraft:beetroot_soup");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(437, "minecraft:dragon_breath");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(438, "minecraft:splash_potion");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(439, "minecraft:spectral_arrow");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(440, "minecraft:tipped_arrow");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(441, "minecraft:lingering_potion");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(442, "minecraft:shield");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(443, "minecraft:elytra");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(444, "minecraft:spruce_boat");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(445, "minecraft:birch_boat");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(446, "minecraft:jungle_boat");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(447, "minecraft:acacia_boat");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(448, "minecraft:dark_oak_boat");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(449, "minecraft:totem_of_undying");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(450, "minecraft:shulker_shell");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(452, "minecraft:iron_nugget");
+                net.minecraft.util.datafix.fixes.ItemIdFix.ITEM_NAMES.put(453, "minecraft:knowledge_book");
+
+                net.minecraft.util.datafix.fixes.ItemSpawnEggFix.ID_TO_ENTITY[23] = "Arrow";
+                // CraftBukkit end
             }
         }
     }
