RE: 20 rep, squats..... curls?
other than deads not really. the whole philosophy behind the 20 reps is the intense breathing that goes with the brutal work and the fact that you have to end up recruiting so many smaller muscles to assist when fatigue sets in. i currently do 1 back off set of deads for 15 reps using max weight and its a real workout on its own.
certainly try it with deads but i wouldnt bother with the rest