this is a funny situational conundrum to be in, but i've definitely been there. i don't mind talking about it.

depending on the character's species, the least obtrusive route would be to simply explore null stuff. failing that... the body shape itself is not the actual issue when trying to put any kind of genitalia on there. it's actually the leg positioning. thigh canyons (such as with boxman, or cuphead, or etc) are inevitably going to look strange and kind of goofy when dangly bits are haphazardly positioned between them.

this body shape, at least in the example you gave, is also inherently pretty toony and unrealistic, so you might as well lean into it. wiggle or completely change the leg positioning situationally, even outside of sexual scenarios. explore different posing and compositional options for cheeky censoring. you can even get silly about things on purpose!

sexual expression does not always need to result in drawings where you can see someone's urethra. sensuality can take so many different forms that have nothing to do with genitalia. this is especially important to keep in mind for designs where slapping a dick and/or balls on them could just end up looking undignified. for example, i think magnemite is very cute, but i have zero desire to see any kind of explicit genitalia on the thing. but there are fun features and analogues to explore with it instead—maybe it likes having its screws touched? maybe it can vibrate. maybe it feels some kind of way about magnetic attraction. electroshock. et cetera.

but at the end of the day, you're your own best judge of what you find sexy or compelling. i'm just some weirdo on the internet. good luck!