Place it at the start of a ninja reveal, then follow it with a jump and a pew pew burst to sell the transformation. For a bigger reaction, add an anime-style wow after the entrance, keeping the ninja line as the setup for the rest of the scene.
About this sound
This short voice clip says 'I want to be ninja' in a bright, eager tone, lasting just under five seconds. It sounds like a playful declaration from someone dreaming of stealth, speed and secret missions. The line feels funny and earnest at once, giving listeners a quick burst of childlike excitement and confidence.