And what did we learn from this?

It would seem that River is able to fit into a space 2.25 inches wide.  So begins another great adventure...

Until she encountered the non-sliding portion of the sliding glass door...

And then depression set in when she realized that she could go no further and had to turn back...

Only to discover that reverse is not her friend. 
Bunnies are ill-equipped to hop backwards.  I laughed way harder than I should have at this.  Even her cheek fur is being smooshed the wrong way!

After her awkward escape from the slider, she was consoled by Simon and all was right with her world again.