4 ideas
A supercomputer spends 7.5 million years calculating the answer to life, the universe, and everything, and produces the number 42 — which is useless because no one ever formulated the actual question. The bottleneck on meaning is not computational power but the framing of the problem itself; an answer without a well-posed question is empty.
A creature placed in the ear instantly translates any language, removing all barriers to understanding between species. The result is not harmony but more and bloodier wars than anything else in the universe, because the obstacle to conflict was never misunderstanding — perfect comprehension reveals incompatible interests rather than hiding them.
Earth is revealed to be a giant computer commissioned by mice, and humanity's entire history is incidental to a calculation it never knew was running. Viewing human concerns from a galactic scale exposes how much of our perceived importance is local self-flattery rather than objective standing.
A towel is presented as the single most useful object a galactic hitchhiker can carry, signaling competence to others who assume a towel-owner must also have the rest of their gear. Survival in an unpredictable universe depends less on controlling events than on signaling and maintaining basic readiness, which compounds into others' trust and assistance.