Can a fixie bike fit in backseat of 2door integra?

Most likely not, make sure to bring an adustable wrench to remove the front and rear wheels, and a metric allen key set to remove the seatpost and you might have a chance, still, without listing the dimensions of your trunk, it is impossible to say. I have managed to put a bicycle in a 2-Seater Nissan Z before, the wheels went in the "trunk", and I wrapped the frame in a blanket and it sat in the front seat, it was still a tight squeeze, but I made it work.

it might fit between the seats

it would in a 4 door car

i mean it would still fit but getting it in will be more awkward

you do have to take the front wheel off

so if it;s all hipsterish and 'tracky' it may be bolted on

wle.

probably if you take the wheels off, and possibly put the seatpost down too.