Incomplete List of D&D Related Things that Are Hard to Imagine

An important aspect of tabletop RPGs that is insufficiently discussed is the theatre of the mind. When playing a game, we - players and DM alike - picture a great variety of things in our minds' eyes. We visualise what ths room looks like, what this monster looks like, what this NPC looks like, and so on. No doubt we also do it when reading splatbooks and modules: we picture in our heads what is not depicted for us in illustrations. But we don't talk a great deal about how this mind's-eye aspect of play works, how to improve it, and what its implications are.

As a very small preliminary matter, there are certain things that I have always found it hard to envisage - things that, when I try to picture in my mind's eye, I always find either look silly, or actually impossible to make concrete, and I was curious whether readers have their own examples to add. Here are some of mine:

• Bird men which wield objects. If a bird man only has four limbs (i.e., two wings and two feet) then it has to wield a weapon or pretty much anything it cannot hold in its beak with its feet. But the idea of a bird man using one foot to swing a sword or hurl a javelin or whatever is faintly ridiculous. 
• Dragons, or other creatures without primate-style mouths, which speak. How does a dragon's mouth move when it talks? What does that actually look like?
• Melee combat between creatures of obviously very different sizes (a human against a hill giant; a human against a sprite). What does it look like for a hill giant to hit a human with its 12' long club and for that to not kill or at best completely incapacitate that human? How can a human slashing away at a hill giant's knees with a sword that in relative terms is a bit like the short blade on a Swiss army knife do enough damage to eventually kill it?
• A fight against a gelatinous cube, or indeed any other amorphous jelly-like object. Slashing a big jelly with a sword is readily visualised. But slashing it with swords until it dies is not. Let alone stabbing it with spears or beating it with maces or whatever. You can imagine pieces being gouged out of it, or cut off, but that would imply a reduction in HD which the rules don't facilitate. You have to imagine the jelly retaining structural integrity but being 'wounded' enough times to give up the ghost.
• A rakshasa's hands are the wrong way round. Really difficult to envisage.
• A person being slowed or hasted. This is not hard to envisage, but hard to envisage and imagine it with a straight face. It is difficult to imagine somebody being hasted without Benny Hill music playing in the background. And it is difficult to imagine somebody being slowed without it looking like silly for-laughs slo-mo like in Zoolander. 

You may very well have your own.