Boggarts & Riddikulus

[Lliannanshe]

No: HPFGUIDX 102162

Barbara said:

 in the initial lesson he gives to Harry's class, Lupin 
uses "Riddikulus!" on his own boggart (the moon shape)and it turns 
into a cockroach (I've no idea why that would be funny, as it is 
supposed to be to fight a boggart). 
<snip>
Harry fights it a few times in training with Lupin and I think he 
passes out a few times and Lupin always forces the boggart back into 
the trunk. Even after HP produces a decent Patronus, Lupin jumps in 
front of the boggart, he yells "Riddikulus," it turns into an orb 
again and then he forces it back in the trunk again. 

Lliannanshe:
Remember, Lupin "almost lazily" turned the orb into a cockroach 
giving Neville the second chance at the boggart. (POA PG139) and, as 
you pointed out, Lupin is able to force the boggart in the trunk 
even in as it is in the shape of an orb.   

Barbara Said:
"What you need to do is force it to assume a shape that you find 
amusing." POA 134
<snip>
However, in GoF, when Harry meets the boggart-dementor in the maze, 
he performs the Patronus Charm, and then realizes that he's not 
fighting a dementor, but a boggart and uses the Riddikulus charm.
<snip>
"There was a loud crack, and the shape-shifter exploded in a wisp of 
smoke." GoF 623

Lliannanshe said:
(OOP PG176) "Lupin waved his wand once more and the orb vanished in 
a puff of smoke"  Lupin is also able to make a boggart disappear 
without an amusing shape change or laughter. We should appreciate 
Harry's level of power.  For Harry, confronting the boggart itself 
was amusing (riddikulus) when compared to confronting a dementor. 
(Puff, in a wisp of smoke)

Lliannanshe 
(Who would like to know if Barbara has any thoughts to add because 
she is on the right track)