Illusion
Optical Illusion
You thought you memorized what this picture looked like, but suddenly everything looks confused and different. That's because it's an illusion.
さっかく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
それがまるで自分のもののような錯覚に襲われたんです。
I was assailed by an illusion that looked just like me.