E.T. is a story about the friendship between Elliott and E.T., neither of whom are exactly what we'd call tall. They're more Spud Webb than Manute Bol. It's fitting, therefore, that the film frequently employs low camera angles that present the action from E.T.'s and Elliott's points of view.
This vantage point is established almost immediately. In the forest, we gaze at the giant trees, witness a car pull up, and peer through the brush at the suburbs below, all from E.T.'s perspective. Moments later, when Keys chases E.T., that's shown from E.T.'s viewpoint, too, with lots of quick cuts to Keys', well, keys dangling and jangling from his belt.
In fact, we don't even see Keys' face until close to the very end of the film. Elliott's science teacher is treated the same way. The camera never veers above his elbows; it stays at Elliott's eye level. The intentionally low camera angles establish adults as imposing and even threatening.
Halloween is shot from E.T.'s squat perspective, too, as he fixates on the fake knife through Michael's head and appraises Mom's semi-risqué costume. (He digs it.) All of these deliberately low camera angles put the audience in Elliott's and E.T.'s positions, causing younger viewers to further identify with them and encouraging older viewers to remember their own childhoods.