I have accidentally put 2SB186 (PNP) instead of NPN Ge transistor in my fuzz face (first position, second one is AC187 NPN), and it seems to be working. How is it possible? 

QuoteI have accidentally put 2SB186 (PNP) instead of NPN Ge transistor in my fuzz face (first position, second one is AC187 NPN), and it seems to be working. How is it possible?

Two things to know:
- If you swap C and E of a transistor it works like a transistor with lower hfe.   (NPN stays as NPN, it doesn't change the type.)
- If you have an NPN CE amplifier and you put in a PNP the CE amplifier becomes a buffer.

The DC biasing might a little wacked but if you just have buffers then there's some slack as far as biasing goes if the signal is small.

OK, but I have put PNP instead of NPN (and didn't rotate pins, so E->E, B->B and C->C), but it still works?

Does it work like it was supposed to do (like a JH1, JH2, Fox Tone Bender, etc) or just some kind/level of sound comes out of it..??

The sound is different, I will post oscilloscope screens soon. One more question - when measuring bias, shall I do it with or without input signal? I presume without.

If so, Rob already answered your query.. 

You have a misbiased CC amp (Emitter follower) in front of a "normal" CE amp..

And yes, we measure DC bias (without any incoming AC)..