#also fire lord liu kang's reaction would be a migraine because he did not asked for the weird stuff happening in his timeline...

[cienie-isengardu]

what du think everyone react if bihan turen into a cat

Those who thought that Bi-Han turning into a cat would solve the problem deeply regretted their optimism once it became clear that cat Bi-Han is much more troublesome and destructive than the human one. 

Kidding! (but only a little…!)

I assume the general reaction would be either confusion, seeing it as some sort of well-deserved punishment in case of MK1 (post-betrayal) or trying to seize the chance and kill their enemy. All depending on which timeline and which Bi-Han we are talking about. For example, old-timeline Kuai Liang and Tomas would have a strong protective instinct to take care of a brother/companion turned into a defenseless animal (Said defenseless animal is totally capable of murder even in cat form, but how quickly they figure it out is of course up to debate). MK1 Kuai and Tomas may argue a lot about how to approach and solve the problem - or rather if they should try to reverse the change at all - if the transformation happened post-storyline.

However, I feel like there are three characters that would react in similar fashion no matter which timeline they came from:

Shang Tsung would definitely be interested from a science point of view. Was that because of magic? New shape-shifting skills he has never heard of before? Also, unless he badly needed Bi-Han’s service in assassination, he would be amused by the situation... At least amused as long as cat Bi-Han is not devastating his laboratory on purpose.

Johnny is gonna be joking about the change non stop but may stop if he treasure his life at all. 

Bi-Han like Bi-Han, he would adapt and perfect his new cat skills while figuring out what to do and how to undo the change.

Everyone else is a fair game I guess, all depending on which Bi-Han we are talking about.