Old and often used stock phrase with several different variations. The first and most commonly used variant is someone telling another person that the other person reminds them of themselves, especially if they add "When I was younger" onto the end of it. In particular The Hero may say it to a character like a Sidekick, a Hero Worshipper or a Non-Action Guy who just showed some pluck and Got Dangerous, an Innocent Bystander who actually helped out, etc. Most commonly used to show that even if a character is outside the Competence Zone currently, they have potential they may yet fulfill, or that they may grow up to be just like the hero and take up the call.