Sniff it. Inhale it. Breathe it. Noooooo... that's not right. Oh yes: ventilate! If you've started down the path of building your own R2, then you're probably a little crazy and need all the grey matter you've got left. So ventilation is key when playing with these glues. If it can melt plastic, it'll do not nice things to your lungs.
R3-Y2 had a couple seconds of screen time in ESB.
I've had a lot of fun making this droid. I got to play with him at Star Wars Celebration V, but had to sell him shortly afterwards due to my kid being born. The guy who got it didn't want the dome, so I still have that.
After reading a particular MAKE Magazine article... I REALLY wanted to strap a small engine to my bicycle. Thus began one of my more mechanical projects.