This works in every possible port of CvS2 (I’ve personally confirmed it on CvS2 for Ps2, Arcade, and even CvS2 EO for Xbox).
To Choose Bison as your Mid-Boss:
Taunt once (and only once) while fighting the AI, and you will always fight Bison as a mid-boss, as long as you fulfilled the normal point requirements for getting a mid-boss. It doesn’t matter if your taunt is interrupted. This works 100% of the time.
I have no idea how to guarantee a fight against Geese.
Thanks, that is all.