I'm currently updating my (own) Minecraft 1.8.8 client (Optifine).
The problem is that there are errors in the net.minecraft.client.renderer.entity package. Below in the following classes: RenderDragon, RenderEnderman, RenderPlayer, RenderSheep, RenderSpider and RenderWolf.
The Optifine version is H8 (1.8.8).
Do you have other mods installed?
Which error is displayed in the error log?
Why are you not running the latest version of Optifine HD U I7 for 1.8.8?
Just do it all