Conversation so far:
What was giant killer and why was Rey Mysterio called that?
Rey Mysterio became a giant killer by defeating large opponents such as Kevin Nash, Bam Bam Bigelow, and Scott Norton.
when was Rey Mysterio's unmasking?
In 1999, Rey Mysterio lost a Hair vs. Mask match, forcing Mysterio to remove his mask.

Question: what happened after that?
Self-contained rewrite: what happened after Rey Mysterio's unmasking?