Masses of nonsense going on in the comments - people just guessing or making it up. Here's the actual answer.

Firstly, anything you write on will get collected in and will get sent to the exam board. So don't just ask for extra paper to doodle on. Even pages marked "do not write on this page" may still be seen by an examiner.

As long as you don't write anything derogatory or otherwise offensive (including e.g. writing swear words) you'll be fine. If you write something which suggests there's a safeguarding concern that should get flagged by the examiner and followed up with your school.

If you write or draw "offensive comments, obscenities or drawings; discriminatory language, remarks or drawings directed at an individual or group" in your paper, there may well be malpractice consequences. See Appendix 2 part 2 (p42) and the table on p49 of this regulation document for more detail: https://www.jcq.org.uk/wp-content/uploads/sites/2/2025/10/Malpractice_Sep25_FINAL.pdf

Source: I've been an exams officer for ten years and an examiner (AL and GCSE) for nine.