zombie84 said:

In this case, it is more likely a convenient way of ILM recycling old effects elements for convenience sake. ILM tends to do that, take an old effect, add some new things so it doesn't look quite the same. This happened in the newer Star Wars a lot, especially in the SE. The shockwave from Alderaan and the Death Stars was an element laying around from Star Trek VI, and the rontos that you see everywhere are just the CG brontosaurus' from Jurassic Park, distorted and repurposed to look more bizarre.

So, when they had to make some kind of magical, bubbly shield device for Harry Potter they just dusted off the Gungan shield and made some minor modifications to it.

Ah, thanks!
That was very helpful, I didn't really know that - resuing techniques/software or stock footage, sure, but not that.

So yea, should've read up that ILM had a part in the movie first :)