Effie in Dreamgirls has to be played by someone overweight.
Isn't Piangi in Phantom supposed to be overweight?
Some characters, while not specified, CLEARLY need to be played by people of certain weights. For example, the dancers in A Chorus Line can't be overweight - it would make no sense (though a cast of ALL overweight actors might actually be interesting...) It would give a whole new meaning to Dance Ten, Looks Three...
Overweight gangs in West Side Story aren't going to cut it.
There are some roles I don't think it would matter in the least - like Henry Higgins, Daddy Warbucks, or the King of Siam, but I don't think you're going to do very well with a large Eliza Doolittle or a chubby Curly in Oklahoma.
Hi, Shirley Temple Pudding.