A twidly knob is the humorous version of male yodler (i.e. dong). Commonly mistaken for a twiddle stick, or a regular knob. The difference between a twidly knob and these other two misconceptions is that the twidly knob is usually half if not a quarter of the size of a twiddle stick or a knob.
1. Hey Mum, I saw that Joel kid's twidly knob today!
2. You know what James, I'd prefer a hefty twidly knob over a pair of juicy twidly tits.