Joey Fatone Says 'Masked Singer' Finale Shocked Him Too, Totally in Dark

Joey Fatone says 'Masked Singer' producers had him, and all the other contestants, jumping through hoops all season to conceal their identities ... even from each other!

The 'NSYNC singer tells us just how extreme their evasive tactics got -- agents, managers and security guards were all wearing masks too. If that sounds like a pain in the ass to you, think again ... Joey says it made shooting the singing competition a ton of fun.

If you're one of the few who missed it ... Joey competed as The Rabbit, singing big hits -- including Ricky Martin's "Livin' La Vida Loca" -- all season.

At one point, he tells us he was onstage with the other 'Masked Singers' -- eventually revealed to be Rumer Willis, Gladys Knight and T-Pain -- but could only guess who they were ... just like the judges and viewers.