How do I remove a brass pipe that has been jammed into a larger iron pipe?
I'd slip a cheater bar into the drain and see if you can pop it loose by turning it clockwise (so you don't unscrew the tail-piece).  If you can get it to turn without twisting it you should be able to get it to pull out. If you can't and it starts to twist the pipe without breaking it loose, cut it off with a hacksaw close to the tail-piece leaving enough of outside to grab with a pair of vise-grips.  Then take a hacksaw blade and carefully cut through the pipe from the inside.  You should then be able to use a vise-grip or pliers roll it in to a smaller diameter and pull out the last bit.