* "He shot up like a weed." This compares the rapid growth to the fast and unexpected growth of a weed.
* "She grew taller overnight, like a beanstalk." This draws a connection to the magical and rapid growth of a beanstalk in a fairy tale.
* "His legs stretched out like a spring uncoiling." This emphasizes the sudden and dramatic lengthening of limbs.
* "He grew taller by the day, like a tree reaching for the sun." This simile highlights the continuous and upward growth, like a tree reaching towards the sky.
Ultimately, the best simile will depend on the specific context and the desired tone.