Reviews of the effect:

From the New York Times - Nov. 14, 1997:
"...you are unlikely to forget such sights as the face of Simba's dead father forming itself into an astral mask among the stars"

From the Daily News - Nov. 14, 1997:
A kid who was interviewed says" ..I really liked when Mufasa's face came out of the stars like it was in 3-D. It popped out of the whole theater."

From Back Stage - Nov. 14, 1997:
"Watch for the highlight -- you won't miss  it -- when Simba sees the image of his father in the reflecting pool.*  Just watch it and thrill and wonder.  For me, it was like the stab of pleasure/pain felt when I first went to the theater as a child, saw the lights and, somehow tear-stained, knew I was hooked for life."

*The beginning of the effect, which ends with the Father coming out of the stars...