Safety Pin!

We have a problem lately with Sophie at bedtime; its actually a big problem that started back in August and now we are beyond frustrated.   The problem is that Sophie takes off her PJ's and diaper when we lay her to bed.  We first started to fix the problem by taping the diaper; we quickly moved through all types of tape and even used duck tape but were quickly outsmarted on all kinds.  The diaper would be off no matter what type of tape was used.  The next idea we had was to use a safety pin on the zippy PJ's and to only put Sophie in zippy PJ's.  This solution worked for a few weeks until one night we poked in to check on her and she was sitting naked in her crib.   We asked Sophie what she was doing and she replied, "playing with a pin,"  holding the pin in her hand for us to see.  The mangled and bent pin was sure enough in her hand; we thought maybe it was a fluke on our part and we didn't attach it right.  Sure enough, night after night the pin has come off.  We are SOOOOOOO sick of stripping the bed and washing the sheets daily and stripping you down for daily baths.   We aren't sure what step to take next to kick this habit....HELP!!!!