Randall doesn't have a hemipenis (well, that's how I like it, it's my NEURON ACTIVATION). He has a cloaca. I thought for a long time about how he would achieve orgasm from sex, and I came up with this interesting anatomical feature – an internal ridge (crista cloacae ventralis interna), the friction of which causes intense arousal and eventually orgasm. You can't just accidentally brush against it, but if you're actually having sex or intentionally rubbing it => the above-mentioned effects occur
