I love this show! It's my guilty pleasure and even DH watches it! Kids are of no help though 
I suggested Justin Hawkins for Chameleon last week and DH said no way, he gets to wash up tonight for that!
Unicorn - Jake Shears! Grew up on a small island, moved to New York, used to tap dance, lots of references to boots in his song choice, recently been in Kinky Boots.
Queen Bee is definitely Nicola Roberts - was the wildcard in Popstars: The Rivals, stands up for what she believes in - very anti bullying, law - after her BBC programme, she petitioned, and won, for tanning beds to be banned for under 18s, beat the drum in her VT was a nod to her album and the whole background was orange (or ginger?) for her performance!
Duck - this one puzzles me, thought it was Paula Radcliffe and am still not convinced that it isn't, especially as her background was gold for the sing off! She also holds her arms a lot like runners do when they finish.
Hedgehog - Micheal Ball. Was in phantom, hairspray (wore heels for nearly two years), also in rocky horror (heels!), great singing ability and is "the greatest showman".