Penjelasan:

plot convenience is a method of story-telling that forces unlikely events to take place because the story calls for it.

In the anime dragonball, Goku as a child transforms into a great ape twice within a year, the first was when they were trapped in 3 foot "special steel" thick cube prizon with tempered glass up on top, the full moon is out, and after he transforms he has his tail cut off.

plot convenience kicks in during the final round of the world martial arts tournament, Goku's tail grows back during his fight with Monster Beast Giran, and the full moon just happens to be out during the final fight. In other words plot convenience happens when coincidences must take place in order for the plot to advance.