1/ being the smartest character/actor 6/ being the dimmest...
I would probably suggest
1/Dr Ross 2/Chandler 3/Monica 4/ Its a throw up between 4 and 5 either Phoebe or Rachel - I guess Phoebe - she must need somekind of qualification for her job. 5/Rachel 6/Obviously baby kangaroo
Any one else agree with the above.
In real life I would have to say 1/Lisa 2/Now I begin to struggle....