Pretty much anytime Mr. Chan is able to catch the real culprit. Hey, he's still the one and only Charlie Chan, after all!
In "The Bronze Idol" Flip was the one to catch the culprit (with some help from Chu-Chu, Scooter and Mimi). Considering he's the one who's most gung-ho about solving the cases and had already been wrong twice in that ep, he had to be feeling pretty damn good about himself right then.
From episode 5: "You stay here, Anne, you're just a girl." "Am what?!" * jumps over the fence, surfs on a wooden board across the lake*
Anytime the kids work together to capture the culprit. Teamwork for the win!
Hoppy the kangaroo knocking Mr. Whitefield to the ground and detaining him in episode 16.