Here is one that is guaranteed to have you yelping, swearing and itching during and after your scene.
Get a pair of pants that is somewhat loose and hole / zipper free, not too tight, some wide rubber bands big enough to encircle your thighs somewhat tightly and or your ankles and a stretchy belt. No underwear will be worn for this!
The to do some prep you need a bucket, a mason jar and a small shovel as well as a pair of rubber gloves.
Go out into your yard or a nearby area with dry exposed dirt and find an ant mound. Fire ants are the preferred type here. Open the mason jar and put on the gloves. Plunge the shovel into the dry dirt a few inches away from the entrance hole. Wait a few seconds for the ants to start streaming out and put the scoop of dirt with ants into the bucket.
Shake the bucket to get the ants and dirt somewhat separated and then tip the bucket sideways over the mason jar. Tapping the bucket to keep them from climbing up catch a few dozen ants in the mason jar. More if you are a real masochist. Once you have ants and not much dirt in the jar put the lid on and dump the dirt back onto the mound.
Shake off the ants from the bucket and your shovel and return to your lair. You now have your punishment waiting in the jar.
During scene prep, put the pants on and pull the rubber bands up over your knees to mid-thigh. Add the ankle bands to prevent and escaping ants and put on your belt, loosely for now.
Now comes the time to get the ants into your pants. You could use a really cheap ziplock bag 2/3 full of air with the ants inside to let the release be 'accidental' or just dump the mason jar in and belt up.
Lock on the stretchy belt or put on cuffs to prevent early escape before starting a predicament scene that would inevitably lead to popping the bag full of ants.
Some alternative modification would include using a balloon but trying to get ants to slip down a funnel into a limp balloon sounds difficult. Or taking a small amount of sugar solution and rubbing it on your crotch beforehand and letting it dry.
This will end with you having a bunch of any bites, they do not like being rubbed on between fabric and skin.
Do NOT do this if you have issues with allergic reactions to bug bites.
When done, remove pants and hose off outside, you probably do not want mad ants in your house. The pants should keep them in place until you finish.