Ever done two projects/fics/stories at once, using the same main/lead? 

I'm currently doing that right now (although I should be studying for my exam paper tomorrow), and I just realised how completely different the personalities possessing this character of mine. 

In the first, old fic, main/lead plays an overstressed work-a-holic, and is a heavy smoker. 

Contrast to the first type, this second, much newer fic he'll be starring in, has him playing a nosy, frivolous, spontaneous, loud character. 

Complete polar opposites. One's a dark, somber character while the other's a cheerful bloke. 

It just feels... weird, ya know? I feel like it's an ultimate feat to accomplish because I haven't mixed these people up yet. 

Have you guys gone through the same process? 

Have two stories but starring the same characters, only their characters are completely the opposite of the other in the other stories. 

Maybe you guys might even have them playing two roles in one fic, like that person has multiple personality disorder or something. 

Or bipolar...maybe... ?