More than anything else, the aim of movie marketing is to get people aware of a film's existence and basically create "mindshare" in the months leading up to its release.
As a result, marketing campaigns can often kick off up to a year before a film ends up hitting cinemas - present circumstances excluded, of course - with teaser trailers showing off early footage to give audiences a taste of what's to come.
But sometimes the shots featured in trailers aren't actually representative of what the final product will look like - the director might use different takes or colour grade the entire movie differently in the theatrical cut.
And then there are those occasions where shots included in the trailer haven't yet been put through the visual effects phase of post-production.
Though audiences largely didn't know it when these trailers first dropped, they weren't actually seeing the director's true artistic intent: planned CGI was absent from these trailer images because the work hadn't yet been completed.
Whether the shot worked regardless or something felt immediately off to viewers, these trailers all released before the VFX were all locked down...
10. Ghostbusters II
One of the most memorable sequences from Ghostbusters II sees the titular ghost-hunters facing off against the ghosts of two executed murderers, the Scoleri Brothers, in a courtroom.
It's a wild scene jam-packed with imaginative visual effects, such that it's not terribly surprising they weren't anywhere close to completed when the film's first trailer was released.
The trailer shows some scattered glimpses of the brothers wreaking havoc, though one notable shot appears without any substantial effects elements - the prosecution lawyer (Janet Margolin) is grabbed by her leg and dragged out of the courtroom by a ghost.
In the final film the ghost is prominently visible throughout the lengthy shot, but in the trailer image we can simply see actress Margolin - or her stunt double, more likely - being pulled along, presumably by a stunt cable.
Thankfully in this case the omitted effects still kinda work, because it's still clear that she's being dragged around by a supernatural, ghostly entity, even if we can't see it. Clever.