Getting rejected from "American Idol" is bad enough -- but to add insult to injury, TMZ has learned, one ex-contestant also got shut down by OTHER "Idol" rejects ... after asking to join their reunion concert.



Sources connected with tonight's Minneapolis reunion show tell TMZ, Dr. Chris Kammer -- a giant toothbrush-carrying dentist who was cast off early in the season -- contacted the show organizer and fellow reject Caleb Hawley ... to see if they needed an MC.

Caleb wasn't into the idea -- and responded to Dr. Chris via email, writing, "Though I really appreciate your offer to MC, I think we'll hold this one down on our own."

Caleb offered to put Dr. Chris on the guest list for the show -- which also features Chris Medina and Carson Higgins --  but that wasn't good enough ... because we're told, Dr. Chris plans to protest in front of the venue before the performance.

"American Idol" contestant Caleb Hawley hadn't heard of the newest trend in dog fashion -- putting sunglasses on a dog's behind -- but he's sure heard of it now!


After we suggested the idea to Hawley on Thursday night (see below), he posted a Twitpic of his dog Fargo wearing a pair of women's sunglasses on his butt.

You're welcome.