Cut the top off the can. Leave no extra can on it. Then cut the bottom, cut as far up as you think you should. Then glue the top to the bottom as tightly as possible.

That's your main wheel. Then take multiple cans and cut the top and bottom off. Then cut the edge off to match the thickness of the wheel we just made. Do this with 3 or more cans, depending on the size of the wall-e. melt/attach them together using sotering iron or tape. These form the tracks

That's a really cool idea.... Thanx Technopro... But I wonder if the track will move with ease... The three wheels are becoming little complicated to move relatively to each other...