#4 Rey Mysterio wasn't allowed to be involved

When the WWF bought out WCW, they got a lot of young, hungry stars along the way, and there were few more popular than Rey Mysterio.
A beloved cruiserweight in WCW, Mysterio would debut in the WWE in 2002, skipping the entire Invasion storyline, and has gone on to become one of WWE's most popular Superstars of all time.
In fact, the master of the 619 was so popular due to his incredible matches in WCW, that the WWF chose not to include him in the storyline, as they thought fans would be unable to boo him.
This was clearly the right call, as Mysterio has been constantly cheered for his underdog spirit by fans, and has gone on to become one of the company's most decorated champions.
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