https://www.curseforge.com/minecraft/mc-mods/polymorph try this.
In reply to 4powerd1:
Try witchery (1.7.10) , is very old an outdated but there is a port https://trello.com/b/uEqGT8F7/witchery-resurrected
If the name contains + or - erease it (referring to the + or -)
Maybe 48 hours.
if you don't say what did you do with mcreator or the crash log no one can help you
The snapshots of 2021.3 are unstable try using 2021.2