箸が転んでもおかしい年頃
Meanings
1
age at which even the slightest things seem funny; giggly age
A set phrase describing the period (especially late teens for girls) when everything seems hilarious. Often used lightheartedly or nostalgically.
She's at that age where even the slightest thing makes her laugh.
Remembering the time when I was at that giggly age makes me feel nostalgic.