Peeves, Ghosts. and the Common Rooms

[gelite67]

No: HPFGUIDX 128281

I'm rereading SS and at one point, Harry entes the common room after 
hearing Snape in the forest with Quirrell.  The text says that Harry 
made sure Peeves wasn't inside before shutting the door.

I neve paid attention to that before.  I guess Harry could simply be 
making sure Peeves wasn't around, but that's the only time in the 
book when he goes to tell R & H something and looks around for Peeves 
in particular.  So it struck me as odd.

I know Peeves is not a real ghost but is a poltergeist or a force of 
chaos, I believe JKR said.  Does that mean that Peeves would 
be "trapped" in the Common Room and couldn't exit if the door was 
closed?  Can he not glide thru walls like the Ghosts can? He can move 
physical objects, so why not open the door?

And come to think of it, have any of the Ghosts ever appeared in 
their respective Common Rooms?  I suppose they could just be giving 
the students privacy, but somehow, I think not.

I only ask because I wonder if this will come into play if (when) 
Hogwarts is attacked.

Angie