Why were Luffy, Zoro, and Usopp surprised when they saw the Dragon from Punk Hazard?


I wonder why Luffy, Zoro, and Usopp (and also Robin) were surprised when they
saw the [Dragon from Punk
Hazard](http://onepiece.wikia.com/wiki/Animal_Species/Pirate_Alliance_Saga#Dragon)
while the three of them have already seen
[Ryu](http://onepiece.wikia.com/wiki/Ryu), the Dragon that they met on Warship
Island?




Their surprise stems from the fact that the Warship Island Arc is a filler
arc. As [One Piece wiki](http://onepiece.wikia.com/wiki/Warship_Island_Arc)
says:

> It is the first story arc of the series not to be based on any content from
> the manga by Eiichiro Oda, making it the first filler arc.

Another reason might be the fact that they had [encountered a
dragon](http://onepiece.wikia.com/wiki/Sandora_Lizard#Sandora_Lizard) (if you
count it as one) only once before, and didn't expect to meet one on Punk
Hazard.




Their surprise stems from the fact that the Warship Island Arc is a filler
arc. As [One Piece wiki](http://onepiece.wikia.com/wiki/Warship_Island_Arc)
says:

> It is the first story arc of the series not to be based on any content from
> the manga by Eiichiro Oda, making it the first filler arc.

Another reason might be the fact that they had [encountered a
dragon](http://onepiece.wikia.com/wiki/Sandora_Lizard#Sandora_Lizard) (if you
count it as one) only once before, and didn't expect to meet one on Punk
Hazard.

