There is a scene where Helvetica proceeds to eat food and drink with her feet this is probably a reference to Quentin Tarantino (a long-time friend of Robert Rodriguez) who is known to have a foot 'fetish' and frequently uses close-ups of feet in his films.
Near the end of "The Miscommunicators" party, Helvetica says "I wish these casts were off" and the camera cuts (01:05:39) to Toe marveling that his arms no longer have casts, but at the right edge of the frame Helvetica's right arm is still shown in a cast and holding the wishing rock. At 01:05:41 she adds "Not his, just mine", at which point the camera cuts to a shot of Helvetica without casts while behind her Toe's arms are in casts again.
During the initial classroom scene when the teacher is conducting an experiment with catalysts, the "blink contest" girl blinks in a brief moment wherein the aliens are circling the bottoms of the classroom desks, ruining her record.
When Loogie wished to have the telephone gone, he was eating cereal and clearly wasn't holding the rock when he made the wish. The rock was on the table next to his bowl.
No. Shorts (aka Shorts: The Adventures of the Wishing Rock) is based on a screenplay by Mexican-American film-maker Robert Rodriguez, who also produced and directed the movie.