Why does node/%node/random/stuff work? I just noticed this, and I can't find an explanation.

I can go to node/1/45645645/klzkelfkzlef/47z4e5fz56e4f/etc and it'll just show node/1 instead of a 404 page.

The same happens with taxonomy/term/%term/stuff

Somehow, if it doesn't match a valid path (/edit for example) it falls back to just a view of the entity. How? Like, where does this happen? 

Is this normal hook_menu behavior? node/%node exists and node/%node/edit exists, so node/%node/random may not exist but it'll use the callback for node/%node anyway?
Ah, just found it in pretty much the first few lines of menu.inc. It does indeed look one level higher until it finds a match.