sneak.sh

#!/bin/bash

ffmpeg -ss 0:10:57 -i "[Commie] Yuyushiki - 03 [064228A1].mkv" \
  -t 0:0:6 -s 480x270 -f image2 %03d.png

convert -delay 1x15 -fuzz '1%' $(
  # Use `seq` hackery to generate a giant list of frames.

  # Original frames of Yuzuko and Yukari rising behind the bed, followed
  # by Yui snapping her eyes open.
  seq -f "%03g" -s ".png\n" 30 2 134

  # Composite Yui's eyes-open face from frame 118 on top of Yuzuko and
  # Yukari "sinking" back behind the bed -- really the original "rising"
  # frames 30 to 98 sequenced in reverse.
  for i in `seq -f "%03g" 98 -2 30`; do
    echo \( $i.png \( 118.png -crop 132x102+313+168 \) -geometry +313+168 -composite \)
  done

  # Composite Yui's eyes closing -- really the original "eyes opening"
  # frames 98 to 118 sequenced in reverse -- on top of the empty room
  # from frame 30.
  for i in `seq -f "%03g" 118 -2 98`; do
    echo \( 030.png \( $i.png -crop 132x102+313+168 \) -geometry +313+168 -composite \)
  done

  ) -coalesce -layers OptimizeTransparency sneak.gif