the performers are so spot on , it is hard to conceive anyone else in their roles . 
(ROOT (S (NP (DT the) (NNS performers)) (VP (VBP are) (ADJP (RB so) (JJ spot) (IN on)) (, ,) (SBAR (S (NP (NP (PRP it))) (VP (VBZ is) (ADJP (JJ hard)) (S (VP (TO to) (VP (VB conceive) (NP (NP (NN anyone)) (ADVP (JJ else))) (PP (IN in) (NP (PRP$ their) (NNS roles)))))))))) (. .)))
(ROOT (S (NP (DT ) (NNS )) (VP (VBP ) (ADJP (RB ) (JJ ) (IN )) (, ) (SBAR (S (NP (NP (PRP ))) (VP (VBZ ) (ADJP (JJ )) (S (VP (TO ) (VP (VB ) (NP (NP (NN )) (ADVP (JJ ))) (PP (IN ) (NP (PRP$ ) (NNS )))))))))) (. )))