Hello,
for some reason Flans mod keeps on raising errors when i am using it in my mod pack...
Here's where the problem is apparently...
---- Minecraft Crash Report ----

WARNING: coremods are present:
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.133-universal.jar)
CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.36-universal.jar)
ItemPatchingLoader (ItemPhysic Lite 1.1.3 mc1.8.jar)
CCCDeobfPlugin (unknown)
NEICorePlugin (NotEnoughItems-1.8-1.0.5.104-universal.jar)
LoadingPlugin (MinecraftCapes Forge1.8.jar)
Mine and Blade: Battlegear2 (1.8-MB_Battlegear2-Bullseye-1.0.10.1.jar)
MovingWorldCoreMod (movingworld-MC1.8-V1.8.1.jar)
Contact their authors BEFORE contacting forge

// Don't be sad. I'll do better next time, I promise!

Time: 21/07/16 19:52
Description: Initializing game

java.lang.IllegalArgumentException: ID is already registered: 31
at net.minecraft.entity.EntityList.func_75618_a(EntityList.java:100)
at net.minecraftforge.fml.common.registry.EntityRegistry.registerGlobalEntityID(EntityRegistry.java:256)
at com.flansmod.common.FlansMod.init(FlansMod.java:269)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:553)
at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:212)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:190)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:119)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:731)
at net.minecraftforge.fml.client.FMLClientHandler.finishMinecraftLoading(FMLClientHandler.java:316)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:491)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:325)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at net.minecraft.entity.EntityList.func_75618_a(EntityList.java:100)
at net.minecraftforge.fml.common.registry.EntityRegistry.registerGlobalEntityID(EntityRegistry.java:256)
at com.flansmod.common.FlansMod.init(FlansMod.java:269)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:553)
at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:212)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:190)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:119)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:731)
at net.minecraftforge.fml.client.FMLClientHandler.finishMinecraftLoading(FMLClientHandler.java:316)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:491)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:325)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 291518336 bytes (278 MB) / 757477376 bytes (722 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.10 FML v8.0.99.99 Minecraft Forge 11.14.4.1577 Optifine OptiFine_1.8_HD_U_F8 40 mods loaded, 40 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHI mcp{9.05} Minecraft Coder Pack
UCHI FML{8.0.99.99} Forge Mod Loader
UCHI Forge{11.14.4.1577} Minecraft Forge
UCHI CodeChickenCore{1.0.5.36} CodeChicken Core
UCHI MinecraftCapes{3.2} MinecraftCapes
UCHI NotEnoughItems{1.0.5.104} Not Enough Items
UCHI darkevilmac.movingworld.common.asm.coremod{} MovingWorld CORE
UCHI itemphysic{1.1.2} ItemPhysic
UCHI battlegear2{1.8} Mine & Blade Battlegear 2 - Bullseye
UCHI zeldaswordskills{1.8-3.2} Zelda Sword Skills
UCHI bspkrsCore{7.01} bspkrsCore
UCHI Treecapitator{1.8} Treecapitator
UCHI MovingWorld{MC1.8-V1.8.1} Moving World
UCHI ArchimedesShipsPlus{MC1.8-V1.8} Archimedes' Ships Plus
UCHI Backpack{2.0.1} Backpack
UCHI wuppy29_slimedungeon{1.6.3} [Slime Dungeons](Better Dungeons Mod 1.8.jar)
UCHI XaeroBetterPvP{1.8.7} Better PVP Mod
UCHI speedytoolsmod{3.0.0} Build Faster Mod
UCHI chiselsandbits{1.6.2} Chisels & Bits
UCHI customnpcs{1.8.0} CustomNPCs
UCHI MoCreatures{8.0.0.devA} [DrZhark's Mo'Creatures Mod](DrZharks MoCreatures Mod-8.0.0.devA.jar)
UCHI golems{2.09} Extra Golems
UCHE flansmod{5.1} [Flan's Mod](Flan's Mod-1.8-5.1.jar)
UCHI gvc{0.6.1} §aGliby's§f Voice Chat Mod
UCHI InfernalMobs{1.6.6} Infernal Mobs
UCHI jum{1.0.2} Jon's Useless Mod
UCHI lucky{6.0.1} Lucky Block
UCHI more{7.0 beta 2} M-Ore mod
UCHI RadixCore{1.8-2.1.0} RadixCore
UCHI MCA{1.8-5.1.1.2} Minecraft Comes Alive
UCHI moredimensions{1.5} MoreDimensions
UCHI morematerials{1.0.20150301.0} More Materials
UCHI moSwords{v1} Mo Swords Mod
UCHI cfm{3.6} §9MrCrayfish's Furniture Mod
UCHI oceancraft{1.5.1} Oceancraft
UCHI rpcraft{2.0} RP Craft
UCHI saoui{1.5a} Sword Art Online UI
UCHI mymod{1.1} [Swords++](Swords++ v1.1 [1.8].jar)
UCHI TooMuchTNT{3.0} [TooMuchTNT](TooMuchTNT v3.0.jar)
UCHI VocaloidMod{0.0.1} Vocaloid Mod
Loaded coremods (and transformers):
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.133-universal.jar)
codechicken.lib.asm.ClassHeirachyManager
codechicken.lib.asm.RenderHookTransformer
CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.36-universal.jar)
codechicken.core.asm.InterfaceDependancyTransformer
codechicken.core.asm.TweakTransformer
codechicken.core.asm.DelegatedTransformer
codechicken.core.asm.DefaultImplementationTransformer
ItemPatchingLoader (ItemPhysic Lite 1.1.3 mc1.8.jar)
com.creativemd.itemphysic.ItemTransformer
CCCDeobfPlugin (unknown)

NEICorePlugin (NotEnoughItems-1.8-1.0.5.104-universal.jar)
codechicken.nei.asm.NEITransformer
LoadingPlugin (MinecraftCapes Forge1.8.jar)
MinecraftCapes.CBClassTransformer
Mine and Blade: Battlegear2 (1.8-MB_Battlegear2-Bullseye-1.0.10.1.jar)
mods.battlegear2.coremod.transformers.EntityPlayerTransformer
mods.battlegear2.coremod.transformers.ModelBipedTransformer
mods.battlegear2.coremod.transformers.NetClientHandlerTransformer
mods.battlegear2.coremod.transformers.NetServerHandlerTransformer
mods.battlegear2.coremod.transformers.PlayerControllerMPTransformer
mods.battlegear2.coremod.transformers.ItemRendererTransformer
mods.battlegear2.coremod.transformers.RenderItemTransformer
mods.battlegear2.coremod.transformers.MinecraftTransformer
mods.battlegear2.coremod.transformers.ItemStackTransformer
mods.battlegear2.coremod.transformers.ItemInWorldTransformer
mods.battlegear2.coremod.transformers.EntityAIControlledByPlayerTransformer
mods.battlegear2.coremod.transformers.EntityOtherPlayerMPTransformer
MovingWorldCoreMod (movingworld-MC1.8-V1.8.1.jar)

GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.5.0 NVIDIA 353.54' Renderer: 'GeForce 920M/PCIe/SSE2'
Launched Version: 1.8-Forge11.14.4.1577
LWJGL: 2.9.1
OpenGL: GeForce 920M/PCIe/SSE2 GL version 4.5.0 NVIDIA 353.54, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.

Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)

Please Help
BTW: I used the wrong crash report sorry,
Detrix.

The issue comes from the Animal Bikes mod.
Third line of the stacktrace "at noppes.animalbikes.AnimalBikes.registerBike(AnimalBikes.java:402)"

Please report the crash to that mod author.

But I don't have that mod in my pack.