Turning frogs into Prince's and executing fair maidens

Okay tech people, this tech novice seeks advice once again...as follows: 1: In our forthcoming medieval romp (Fairytale of sorts), there's a scene where the Queen is beheaded, now quite selfishly, our lead actor isn't too happy about having her head taken from her shoulders, (I'll give her that it's very pretty head, but whatever happened about sacrifice for art?) Anyway, we picture the scene...there's our pretty Queen head on the chopping block...the executioner ready to bring down his axe...we have an authentic sound effect for the chop, but how best to convince the audience we've done it for real...is it possible to do so without a tacky blackout...one thoguht is we we could screen the execution with the excitable mob of peasants who've gathered for the beheading, however, I'm sure there's been loads of beheadings done on stage, and some of you tech people / set designers will know eactly how we should do it....moving right along.. 2: We have a scene where the Prince is turned into a frog (yes, we just have to be differen), by the witch. The witch of course has our dear Prince leaning over the caudron as she mutters her spell, followed by a wave of the ole magic wand, and hey presto....bugger it didn't work, let's do it againn...actually it will work, and at time of the change, it would be great to have a puff of coloured smoke (???) and other such trickery (lights etc) ....as per above, can anyone suggest a 'how to pull this off and have the audience gasping words such as?, 'Did you see that?' Well no, actually I didn't... PS: Feedback translated into non-technical jargon would be appreciated. ta Johnny Grim