"Ode to the Brain", Symphony of Science,
by Melodysheep. YouTube version here.
"Alone in My Room", Abstruse Goose.
"NUMB3RS", Abstruse Goose.
"Demonic Encounter", Abstruse Goose.
"Teaching Physics", xkcd.
"Astrophysics", xkcd.
"Choices, Part 2", xkcd.
"Rite of Passange", Abstruse Goose.
"Criticism", Abstruse Goose.
"Supernova", Abstruse Goose.
Calvin and Hobbes
PHD Comics: Pro and Con
PHD Comics: Your Shrinking Sense of Humor
PHD Comics: Your Math Skills
"Linear Regression", xkcd
"Fancy Pancakes", Foxtrot
"Don't worry, you'll learn it later", Spiked Math
“d(Pain)/dt”, xkcd
“Lower case xi?”, Spiked Math
Full comic at PHD Comics: “Tales from the Road -- Princeton”
“Espresso”, SMBC