The meme brilliantly combines planetary astronomy with internet culture. Mercury in prograde is just regular Mercury, minding its own business, orbiting the sun as expected. But Mercury in retrograde? That's when the planet appears to move backward in the sky from our Earth perspective, and apparently it's also when Mercury puts on pixelated "deal with it" sunglasses and gets sassy. Astronomers spend years studying orbital mechanics only to create memes about planetary motion being responsible for their bad day. The retrograde motion is just an optical illusion caused by relative orbital positions, but try telling that to Mercury when it's in its moody phase.