Place it right after the fall in your edit, following Cartoon Slip for the tumble and before Sudden Suspense for the aftermath, then finish with Oh My God Wow as friends react. That order keeps the joke clear: slip, numb legs, tension, then surprise.
About this sound
This very short spoken clip delivers the line about not feeling your legs in a strained, pained voice, lasting barely a blink. It lands as sudden, comic distress, the kind of over-the-top hurt that makes a small fall feel dramatic. Listeners hear instant shock and exaggeration, perfect for reacting to a clumsy tumble without saying a word yourself.