Hat of Disguise

[Caliban]

What? No boom? No crackle of energy? I would have least thought that my monitor would have shaken slightly when Caliban posted his reply.

 

[Savage Wombat]

Also note...

... that just because you make the Will save and detect the illusion doesn't mean you see through it. Just that you're aware it's an illusion.

Change Self is an odd spell - most glamers are things like Invisibility, that don't allow opponents to save.

When I had the PCs fight Abishai with Change Selfs up, I let them notice brief glimpses of things (like tail attacks!) that violated the image, but they couldn't see what they were really fighting until the Abishai allowed them to.