Contacts and Glasses
A math teacher allowed his students to have a 3×5 card which they could write anything they wanted on one side for their midterms and finals. Most students said they didn’t even need the card, but one student came in with the tiniest handwriting written on the card. The teacher couldn’t read it at all. Turns out, the student was wearing both contacts and his glasses, giving him a magnification effect to read the answers.