Variety reports the specifics: Riggle will be a guest panelist for the ninth episode (airing May 12), with Rucker appearing in episode 10 (May 19) and Season Four winner Rimes returning for the finale (May 26).
They'll join host Nick Cannon, who missed this season's first five episodes due to a positive COVID-19 test and was temporarily replaced by Niecy Nash, plus panelists Ken Jeong, Robin Thicke, Nicole Scherzinger and Jenny McCarthy.
So far, quite the cast of celebrity contestants has been unmasked: Logan Paul (Grandpa Monster (a relative of T-Pain's The Monster and Bob Saget's Squiggly Monster?)), Danny Trejo (Raccoon), Bobby Brown (Crab), Tyrese Gibson (Robopine), Caitlyn Jenner (Phoenix) and even Kermit the Frog (Snail).
The final five masked singers are Black Swan, Chameleon, Piglet, Yeti and the four Russian Dolls. The latter's the series' second multi-person mystery, with the first being Clint and Lisa Hartman-Black as the Snow Owls.
Rucker in particular seems like a huge get for the TV show as it competes with the final episodes of American Idol and The Voice's current seasons. Though not introducing him as the singing and masked Blowfish (as in Hootie & the Blowfish) feels like a missed opportunity.
Last season, Thicke guessed that Rucker was The Banana based on a clue package. The completely unpeeled competitor ended up being Bret Michaels.
The Masked Singer is based on the South Korean TV series King of Masked Singer. The American version debuted in 2019 and already has a spin-off series, The Masked Dancer.