'Masked Singer' Contestant Upsets Other Competitors With Big Entourage

One mystery contestant on "The Masked Singer" isn't looking to make any more friends ... pissing off fellow masked celebs with maybe the biggest entourage ever.

Backstage sources at 'TMS' tell us ... in the past 6 seasons, they've never seen a contestant show up with a crew this big. Usually, celebs roll solo at rehearsals to avoid revealing their identity, but this person seems unconcerned, opting to bring a massive group with them!

Friends, managers, beauty and hair team, family members... this contestant rolls deep.

We've also learned that the sheer size of this celebrity's entourage has pissed off other contestants backstage ... one contestant in a trailer close to them complained to producers about the noise coming from the giant posse ... turning relaxing downtime into a giant headache.

Our sources won't reveal which contestant rolls with the giant entourage -- not wanting to give away who this might be -- so fans will have to come to their own conclusions for the time being.