Horrid Henry's Diary is an episode in Series 1.
- This episode is an adaptation of the story of the same name in Horrid Henry's Bedtime. It also adapts moments from Horrid Henry Eats A Vegetable from Horrid Henry's Underpants, Horrid Henry's Bathtime from Horrid Henry Meets The Queen and Horrid Henry's Bedtime from the aforementioned book of the same name, in respective order.
- This is the only episode to show a shot of someone's posterior, in this case, it is Peter's, as seen when he gets in the bath with Henry.
- This epsiode has the rare event of someone seen naked; in this case, it is Peter as he gets into the bath. His buttocks are shown on screen while he is getting into the bath.
- When Henry is at school, in the diary, there is a little pause between what Miss Battle Axe says!