so in D&D the gelatinous cube is an explicit in-setting ecological representation of the fact that "dungeons with ten-foot-wide corridors" are a common enough feature that there are creatures adapted or designed specifically for them. but dragons aren't adapted for that design at all, nor are a lot of the other big guys; they either need separate exits or to use magic or shapeshift into a human form to go throguh the tunnels
but this is a problem that has been solved in real-life! the problem of "large animal that needs to get into a fairly consistently-sized tunnel that's significantly smaller" is solved by snakes, and, crucially, by mustelids, animals that are very long relative to their size. so I think D&D needs more of that. there should be giant ten-foot-wide dungeon weasels and stuff.
I love everything this post is laying down, but let’s not zoom past the most important possibility.
Square dragons.
My dumb ass really thought I was gonna be able to scroll past this post without drawing the two most ridiculous dragons to have ever infested my brain.
