Charlie Was Never On Set
Throughout the entirety of the show, the character Charlie never appeared on screen. You would only see the back of his head or the back of his body. However, even this was allegedly a body double. Kind of reminiscent of the more modern Home Improvement, where you always only saw the neighbors eyes over the back of the fence.
In the case of Charlie’s Angels, not only did Charlie’s face never appear on screen but the actor John Forsythe never even showed his face on set! All of his vocal appearances were actually pre-recorded in a recording studio and dubbed in after. Reports on the reasoning behind his non-appearances are conflicted. Some say that producer Aaron Spelling wanted to keep the mystery of the character and others say that John Forsythe wanted too high of pay to appear on-screen.