Locating pikachu, since he attacked night 1, it's logical he is not to be found among the replacements. That leaves:

Beefy187
Csargo
dcmort93
Diamondeye
johnhughthom
landlubber
pevergreen

Super secret analysis gives:
Chance of being phazon corrupted: Chance of being bowser corrupted:
Csargo 13,67 14,11
dcmort93 19,44 0
Diamondeye 8,33 11,67
johnhughthom 6,89 44,89
landlubber 15,89 0
pevergreen 0,33 24,16
Beefy187 18,44 30,78

Overall mafianess
Csargo 27,78 Probably just a bad innocent
dcmort93 19,44 Probably of team PHAZON
Diamondeye 0 Probably just a bad innocent
johnhughthom 51,78 Probably of team BOWSER
landlubber 15,89 Probably of team PHAZON
pevergreen 24,49 Probably of team BOWSER
Beefy187 49,22 Probably a serial killer

Pikachu == dcmort93

Vote: dcmort93

If anyone can take anyone of the list, do so, we can have pikachu in no time.