from wikipedia:

Casting

Cameron often casts certain actors more than once in his films. Cameron has consistently worked with http://en.wikipedia.org/wiki/Bill_Paxton - Bill Paxton (who also narrated http://en.wikipedia.org/wiki/Ghosts_of_the_Abyss - Ghosts of the Abyss ), http://en.wikipedia.org/wiki/Michael_Biehn - Michael Biehn , http://en.wikipedia.org/wiki/Lance_Henriksen - Lance Henriksen (who also narrated http://en.wikipedia.org/wiki/Expedition:_Bismarck - Expedition: Bismarck ), http://en.wikipedia.org/wiki/Jenette_Goldstein - Jenette Goldstein and http://en.wikipedia.org/wiki/Arnold_Schwarzenegger - Arnold Schwarzenegger .

Actor	Xenogenesis (1978)	http://en.wikipedia.org/wiki/Piranha_II:_The_Spawning - Piranha II: The Spawning (1981)	http://en.wikipedia.org/wiki/The_Terminator - The Terminator (1984)	http://en.wikipedia.org/wiki/Aliens_%28film%29 - Aliens (1986)	http://en.wikipedia.org/wiki/The_Abyss - The Abyss (1989)	http://en.wikipedia.org/wiki/Terminator_2:_Judgment_Day - Terminator 2: Judgment Day (1991)	http://en.wikipedia.org/wiki/True_Lies - True Lies (1994)	http://en.wikipedia.org/wiki/Titanic_%281997_film%29 - Titanic (1997)	http://en.wikipedia.org/wiki/Avatar_%282009_film%29 - Avatar (2009)
http://en.wikipedia.org/wiki/Bill_Paxton - Bill Paxton			Y	Y			Y	Y
http://en.wikipedia.org/wiki/Michael_Biehn - Michael Biehn			Y	Y	Y	Y*
http://en.wikipedia.org/wiki/Linda_Hamilton - Linda Hamilton			Y			Y
http://en.wikipedia.org/wiki/Lance_Henriksen - Lance Henriksen		Y	Y	Y
http://en.wikipedia.org/wiki/William_Wisher_Jr. - William Wisher Jr.	Y		Y		Y	Y
http://en.wikipedia.org/wiki/Jenette_Goldstein - Jenette Goldstein				Y		Y		Y
http://en.wikipedia.org/wiki/Arnold_Schwarzenegger - Arnold Schwarzenegger			Y			Y	Y
http://en.wikipedia.org/wiki/Sigourney_Weaver - Sigourney Weaver				Y					Y
http://en.wikipedia.org/wiki/Earl_Boen - Earl Boen			Y			Y

* His reprised role of Reese was cut from the theatrical release, but restored in the DVD's Special Edition Version.

Recurring themes

Throughout Cameron's career, several of his films have had recurring themes and subtexts. These include: the prospects of nuclear holocaust (the Skynet takeover scenario from both Terminator films), ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-newy-53 - [54]} attempts to reconcile humanity with technology (as seen in Aliens and Terminator 2: Judgment Day), humanity repeating the same mistakes, ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-54 - [55]} the dangers of corporate greed, ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-55 - [56]} strong female characters (Sarah Connor and Ellen Ripley being the most famous), ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-Popc-56 - [57]} a strong romance subplot, ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-57 - [58]} anti-corporation (Aliens, Avatar), anti-military (The Abyss, Avatar), and an undercurrent of feminism. This was also present with Jamie Lee Curtis's character in True Lies and Kate Winslet's role in Titanic, in which she served as the main protagonist and narrator.

While The Abyss dealt with deep sea exploration (shot on a studio set), ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-58 - [59]} Cameron himself became an expert in the field of deep sea wreckage exploration exploring the wreckage of Titanic and Bismarck. ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-59 - [60]} Cameron will return to this theme with The Dive (see Projects), shooting from a minisub. ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-60 - [61]}

So important is technology in Cameron's films that he waited years for the technical tools of the craft to advance sufficiently to realize his vision for Avatar, for which he had special 3-D cameras developed. ^{http://en.wikipedia.org/wiki/James_Cameron#cite_note-61 - [62]}