In this case, endless patience :-) This time I removed the CG robot using a custom matte not only of the building but also the background, which in on itself was no easy task, since (and you may not notice this if you're not paying attention to it) the camera moves slightly several times, so I had to track that movement. And then I had to rotoscope all the other elements back in front of the area of where the robot was, sometimes combining GOUT and SE footage, if the robot was composited in front of the character. I can still see some glitches that I just couldn't get quite right but you'd probably never notice those if you didn't study the shot carefully. As it stands, if you just watch it once in the movie, it should hopefully look like the robot was never there and nothing was ever done to the shot.

If anyone's interested, here are a few frames from the project file saved as photoshop layers.