I was trying to see if the mobs were working in a test sever and the copper golem model was a pig and i couldn't find the copper button so i tried to spawn in the tuff golem and it crashed my client and not the sever. I tried re-joining and i was still crashing. any thoughts?

im so sorry its not in my mods folder my bad, have a good day

You need to have mod on both client side and server side.

No worries, happy it is working :).