I used to work production sound recording when I was a lot younger, the sound guys likely unplugged the fridge because the compressors when they're running (on an automatic switch) makes an aweful humm that's a bi!@# to edit out later but can be done... or we just unplug the fridge and get rid of the sound from the recording. Why the microwave was unplugged is maybe because it had a clock on it (the edititor's bane), maybe they unplugged both not knowing which one was the fridge and teh fridge wasn't running at the moment, etc. etc.. The unplugged fridge is SOP, the unplugged microwave is a coin-toss, so a little suspicious but definetley far from unheard of in production recording/filming.
You know that makes a lot of sense and if this were a new show I'd be more inclined to agree with you there. Basically they are taping and someone mentions that having those plugged in may not be a good idea so they unplugged them for the reasons you mention. What bugs me about that theory is that by this point, this show had already been on the air for a number of years and they were in a new facility knowing that cameras would be pointed at them and knowing that having running compressors and digital clocks would be a bad idea.
Basically what I'm saying is that why would they even put a fridge/microwave in a room like that knowing that a lot of filming would occur there? Also if you notice in later episodes the fridge and microwave were never replaced (to that location) which means that they had no specific purpose for being in that room other than for being props to be kicked around.
I'm not saying the entire show was staged, but I can't help but to think that the scene was staged... or at least provoked in some manner. Maybe they had already got into a bit of an argument and Jr had already quit, but the camera crew asked them to do it again and to go crazy with it?? The thing is that we may never know, but the fact that the appliances were there in the first place was already suspicious, and the fact that neither were plugged in especially so.
