Planets do not twinkle.

Explanation

i. The rays of light from a planet pass through the atmosphere of the earth.
ii. As compared to stars, planets are nearer to earth.
iii. So a planet can be considered as a collection of large number of point sources of light.
iv. If the intensity of light from one point source decreases, it increases from the other source. Thus, the average intensity remains the same. Hence, planets do not twinkle.