Fix some load order/registration issues

src/main/java/com/minelittlepony/unicopia/block/UBlocks.java

@@ -24,6 +24,7 @@ import net.minecraft.util.Identifier;
 import net.minecraft.util.registry.Registry;
 
 public interface UBlocks {
+    CloudFarmlandBlock cloud_farmland = register(new CloudFarmlandBlock(FabricBlockSettings.of(UMaterials.CLOUD).noCollision().ticksRandomly().breakInstantly().sounds(BlockSoundGroup.WOOL).build()), "cloud_farmland");
     CloudBlock normal_cloud = register(new CloudBlock(CloudType.NORMAL), "cloud_block");
     CloudBlock enchanted_cloud = register(new CloudBlock(CloudType.ENCHANTED), "enchanted_cloud_block");
     CloudBlock packed_cloud = register(new CloudBlock(CloudType.PACKED), "packed_cloud_block");
@@ -50,8 +51,6 @@ public interface UBlocks {
     StickBlock stick = register(new StickBlock(), "stick");
     TomatoPlantBlock tomato_plant = register(new TomatoPlantBlock(), "tomato_plant");
 
-    CloudFarmlandBlock cloud_farmland = register(new CloudFarmlandBlock(FabricBlockSettings.of(UMaterials.CLOUD).noCollision().ticksRandomly().breakInstantly().sounds(BlockSoundGroup.WOOL).build()), "cloud_farmland");
-
     HiveWallBlock hive = register(new HiveWallBlock(), "hive");
     ChitinBlock chitin_block = register(new ChitinBlock(), "chitin_block");
     Block chissled_chitin = register(new ChiselledChitinBlock(), "chissled_chitin");
@@ -60,17 +59,17 @@ public interface UBlocks {
     SlimeLayerBlock slime_layer = register(new SlimeLayerBlock(), "slime_layer");
 
     Block sugar_block = register(new SugarBlock(), "sugar_block");
-
-    SaplingBlock apple_tree = register(new SaplingBlock(
-            new CustomSaplingGenerator(5, Blocks.OAK_LOG.getDefaultState(), UBlocks.apple_leaves.getDefaultState()),
-            FabricBlockSettings.of(Material.WOOD).build()
-        ) {}, "apple_sapling");
     Block apple_leaves = register(new FruitLeavesBlock()
             .growthChance(1200)
             .tint(0xFFEE81)
             .fruit(W -> TreeType.OAK.pickRandomStack())
             .compost(w -> new ItemStack(UItems.rotten_apple)), "apple_leaves");
 
+    SaplingBlock apple_tree = register(new SaplingBlock(
+            new CustomSaplingGenerator(5, Blocks.OAK_LOG.getDefaultState(), apple_leaves.getDefaultState()),
+            FabricBlockSettings.of(Material.WOOD).build()
+        ) {}, "apple_sapling");
+
 
     static <T extends Block> T register(T block, String name) {
         return Registry.BLOCK.add(new Identifier(Unicopia.MODID, name), block);

src/main/java/com/minelittlepony/unicopia/entity/UEntities.java

@@ -2,9 +2,11 @@ package com.minelittlepony.unicopia.entity;
 
 import java.util.List;
 
+import com.minelittlepony.unicopia.Unicopia;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EntityCategory;
 import net.minecraft.entity.EntityType;
+import net.minecraft.util.Identifier;
 import net.minecraft.util.registry.Registry;
 import net.minecraft.world.biome.EndBiome;
 import net.minecraft.world.biome.ForestBiome;
@@ -38,7 +40,8 @@ public interface UEntities {
     // builder.projectile(SpearEntity.class, "spear", 100, 10)
 
     static <T extends Entity> EntityType<T> register(String name, EntityType.Builder<T> builder) {
-        return Registry.register(Registry.ENTITY_TYPE, name, builder.build(name));
+        name = Unicopia.MODID + ":" + name;
+        return Registry.register(Registry.ENTITY_TYPE, new Identifier(name), builder.build(name));
     }
 
     static void bootstrap() {

src/main/java/com/minelittlepony/unicopia/item/UItems.java

@@ -3,6 +3,7 @@ package com.minelittlepony.unicopia.item;
 import static com.minelittlepony.unicopia.EquinePredicates.*;
 
 import com.minelittlepony.unicopia.USounds;
+import com.minelittlepony.unicopia.Unicopia;
 import com.minelittlepony.unicopia.block.UBlocks;
 import com.minelittlepony.unicopia.entity.UEntities;
 import com.minelittlepony.unicopia.magic.spell.ScorchSpell;
@@ -24,6 +25,7 @@ import net.minecraft.item.Items;
 import net.minecraft.item.MusicDiscItem;
 import net.minecraft.item.TallBlockItem;
 import net.minecraft.sound.SoundEvent;
+import net.minecraft.util.Identifier;
 import net.minecraft.util.Rarity;
 import net.minecraft.util.UseAction;
 import net.minecraft.util.registry.Registry;
@@ -148,12 +150,8 @@ public interface UItems {
     Item juice = register(new ToxicItem(new Item.Settings().recipeRemainder(Items.GLASS_BOTTLE), 2, 2, UseAction.DRINK, Toxicity.SAFE), "juice");
     Item burned_juice = register(new ToxicItem(new Item.Settings().recipeRemainder(Items.GLASS_BOTTLE), 3, 1, UseAction.DRINK, Toxicity.FAIR), "burned_juice");
 
-    static <T extends Item> T register(T newItem, Item oldItem) {
-        return Registry.ITEM.add(Registry.ITEM.getId(oldItem), newItem);
-    }
-
     static <T extends Item> T register(T item, String name) {
-        return register(item, name);
+        return Registry.ITEM.add(new Identifier(Unicopia.MODID, name), item);
     }
 
     static MusicDiscItem createRecord(SoundEvent sound) {
@@ -196,5 +194,9 @@ public interface UItems {
         Item peony = register(new ToxicBlockItem(Blocks.PEONY, new Item.Settings().group(ItemGroup.DECORATIONS), 2, 1, UseAction.EAT, Toxicity.SAFE), Items.PEONY);
         Item tall_grass = register(new ToxicBlockItem(Blocks.TALL_GRASS, new Item.Settings().group(ItemGroup.DECORATIONS), 2, 1, UseAction.EAT, Toxicity.SAFE), Items.TALL_GRASS);
         Item large_fern = register(new DynamicToxicBlockItem(Blocks.LARGE_FERN, new Item.Settings().group(ItemGroup.DECORATIONS), 2, 1, UseAction.EAT, Toxicity.SEVERE, Toxin.DAMAGE), Items.LARGE_FERN);
+
+        static <T extends Item> T register(T newItem, Item oldItem) {
+            return Registry.ITEM.set(Registry.ITEM.getRawId(oldItem), Registry.ITEM.getId(oldItem), newItem);
+        }
     }
 }