#alt mode interfacing

Partner has a wheel kink or something? Turn the sensitivity of those wheels way up and make them an erogenous zone. Same with rotors or wings or whatever.

And they should be able to connect a separate object, whether with wires or maybe a wireless connection. This could be a sex toy or something, but it could also be something like Optimus Prime's trailer. Optimus Prime's partner could be touching the temporarily erogenous parts of the trailer while he is watching from a short distance away or something.

Bonus points if they’re on opposing factions.

Just imagine, human sidekick of a Autobot/decepticon having their body hot just by thinking of the big robot. Panting, huffing, etc as they chase their release of the thought of the alien. And the alien in question is detecting heat radiating from their human friend and worries and confusion fall upon them, thinking "are they getting sick? I swear it's probably that 13th beer doing this to them."

Another case scenario in my mind, is that the human were sleeping inside Autobot/decepticon alt mode before waking up from the fifth wet dream that week and just couldn't hold it anymore so they just start jerking off in there. They whine a little at the bot named, wishing them to fuck, to fill them up. Just anything. The bot (who's in recharge) wakes up as heat start to rise up at the human pheromones, and before they ask "did the ac/fan not turn on?" They saw the sight of their human friend fingering/rubbing themselves or using a sex toy they brought for 'no reason' at the backseat before shooting/squirting load on to the car floor or maybe dripping down to the seat

Sighhhh, Tailgate is one lucky mech