During the development of a theme park attraction, it is normal for a large number of different designs to be put forward. Naturally, not all of these will ultimately see the light of day. However, sometimes concepts can come very close to actually being constructed, before a rapid change of direction completely alters the ride or show.

There are few examples of literal last-minute decisions that have dramatically changed a theme park ride - not surprising, given that they often take three years or more to develop and construct. But, in the case of some attractions that went on to become classics, decisions were made relatively late on that saw them take on a radically different form.

Let's take a look at 5 examples of hugely popular theme park rides that could have been very different.

5. Pirates of the Caribbean (Disneyland)

What it could have been: Pirates of the Caribbean was originally envisioned as New Orleans-themed Blue Bayou Mart. A Madame Tussauds-style Pirate Wax Museum would have have been housed in a 70-foot deep basement, construction of which had already started.

The decision The success of It's a Small World at the New York World's Fair led Walt Disney to decide to transform Pirates of the Caribbean into a boat ride, to allow for a broader array of scenes and a high capacity. At the same fair, Great Moments With Mr. Lincoln proved that Disney could create realistic human figures using audio-animatronic technology, so Walt decide to include some of those, too.

The result: The basement would now serve as the grotto section of the attraction. The wax figures were no longer necessary, with audio-animatronics being used in their place. There are dozens of rides that are inspired by Pirates of the Caribbean, including clones at other Disney parks and inferior copycats such as Pirate Adventure at Drayton Manor in the UK.

4. Nemesis (Alton Towers)

What it could have been: Having acquired the UK's most popular theme park, Tussauds was determined to build a new unique roller coaster at Alton Towers. Fresh from the successful project to add the heavily-themed suspended coaster Vampire to the Tussauds-owned Chessington World of Adventures, Arrow was keen to engage with Alton Towers’ owner once again. This time, it had a new trick up its sleeve: the pipeline coaster.

The chief innovation of the pipeline coaster (and the one from which it derived its name) was the positioning of the ride’s trains. Rather than sitting on top of the track (as with a traditional coaster) or beneath it (as with a suspended or inverted coaster), the vehicles would instead sit in-between the rails. The u-shaped track, with the trains running down the middle of it, had the appearance of a pipeline. Due to height restrictions at Alton Towers, it would be built into a huge pit, and themed around a secret weapon.

The decision: According to Arrow, the early test runs of the pipeline coaster were a huge success. “Awesome”, “smooth” and “totally different” were among the superlatives apparently thrown at the new creation by those lucky enough to try it out.

Problems, though, began to emerge when Tussauds' John Wardley was invited to Utah to ride the prototype. He found it to be a huge disappointment, later describing it as “very slow and rather boring”. The primary issue was the level of friction generated by the ride’s trains as they traversed the track, which made it very energy inefficient. Wardley discovered that Bolliger & Mabillard was building a new type of inverted roller coaster for Six Flags Great America, and opted to use that ride system instead.

The result: Nemesis reused the original idea of burying the pipeline coaster in a pit, but the inverted coaster proved to be a much better fit. The ride has now been open for two decades but remains one of the most highly-regarded and popular coasters in the UK.

3. The Amazing Adventures of Spider-Man (Islands of Adventure)

What it could have been: Universal originally intended for Spider-Man to be a much simpler attraction. According to Ben Lovelace, who worked on the ride, it was initially conceived as a basic dark ride, with a chain of cars passing by a film of some sort. This has been confirmed by Gary Goddard, whose design firm worked on an early version of the ride that would have used a similar ride system to Disney's Omnimover attractions (such as the Haunted Mansion).

The decision: When in 1995 Disneyland opened Indiana Jones Adventure: Temple of the Forbidden Eye, combining an innovative motion vehicle system with stunning special effects, Universal felt it needed to up the ante. "We always try to make things a little higher, a little faster, a little bit more dynamic, so we have something to market technologically," said Lovelace. "Universal pushes the envelope." Universal instead decided to incorporate elements from two previous rides - Back to the Future: The Ride (which featured advanced motion simulators) and Terminator 2: 3-D (which combined 3-D projection screens with physical) effects.

The result: A ground-breaking dark ride that combines moving, motion-simulating vehicles, 3-D projection screens and physical effects to take riders on an adventure with Spider-Man himself.