Wow. Who'd have thought that after 25 years of sitting in someone's stomach the humble felt-tip pen would still work -- but it's true.
This remarkable story of a felt-tip gone rogue was reported in the British Medical Journal, after a 76-year-old woman complained of stomach problems. The poor woman had accidentally swallowed said pen when attempting to poke a spot on her tonsils, as you do, 25 years ago. Neither her husband, nor her doctor believed her; and when abdominal X-rays didn't reveal the stealthy writing implement, it was forgotten about.
The pen was removed after being shown by the more modern CT scan and incredibly it still worked. My shoddy pens normally dry-out and cease to work within hours of leaving the top off, let alone if I swallowed them and let them nestle within my gastric juices for 25 years. Stomach acid is pretty powerful stuff, but maybe it's the secret for preserving those permanent markers you only use once a year.