I thought you might do something like that.  You set it up really well, too.  You successfully evaded many cliches, which is very much appreciated.  Bobby putting those quotes together in his head was a nice touch, as was his self-imposed slowness to catch on to what it would take to make Jen big.  I really liked Bobby's reactions to his new height as well.

The dialog is impressive, as always.

You've left yourself lots of room to write.  I have no idea what Sara has in store for poor Bobby.  i mean, I know she won't hurt or torment him, but I don't think she's above having a little 'harmless' fun at his expense either.   Also, It'll be neat to see how Jen experiences the world through her new perspective.  I've got a feeling it'll be a while before Bobby gets back to her, though.