​ Out on the road were clouds of Professors and Mrs. Flittersnoops.  A real    policeman stopped and gaped at the half policeman, who shouted ‘Pass along please…’ for the last time and then went  zzzp back in to the photograph he had come from, with the Professor aged twenty.
a) Why did the real policeman stop and gape at the half policeman?
b) How did the clouds of Professors and Mrs. Flittersnoops end up on the road?
c) What is the figure of speech used in the following line? ‘……for the last time and then went zzp back……