- Expanding Roster: New characters that weren't even mentioned in the first movie are introduced in the sequels to become vital to the mythos or there is a new running plot that wasn't even a glimmer in the first movie yet dominates the other two. These new characters and plots may end up taking air away from the characters that the audience fell in love with in the first movie, or the writer may end up preferring them to the original characters; they may end up becoming The Scrappy or a Creator's Pet.
- Breakout Characters: Characters who had only minor roles in the original movie, but those scenes proved immensely popular with viewers are likely to be given bigger roles in the sequel, in the hope to capitalize on their success. However, it may be the case that when it comes to these characters less is more.
- Required Cliffhanger: Where the first movie might end with all the loose ends tied up, the second movie often ends on a Second Chapter Cliffhanger or Sequel Hook ending that is just designed to get audiences anticipating the final installment of the trilogy. This can have the unfortunate side-effect of appearing too contrived or rendering the events of the second movie largely pointless if a potential conclusion has been in reach, only to be snatched away a cruel twist of fate in order to set up a cliffhanger for and justify a third movie.
- Exaggerations: This is especially the case if they begin to drift further and further from the elements that made the original such a charming hit with the audiences, or - and in some cases worse - begin to rely too heavily on Pandering to the Base or over-Flanderization of the main characters and story.
- Ret Cons: If Part One is too stand-alone and / or doesn't possess any Sequel Hook, then a Sequel Reset may be required to open up the plot for Parts Two and Three, which presents its own problems.
- Too Little Story: The story seems stretched too thin between Two and Three, with lots of Padding that slows the story down, a Wacky Wayside Tribe or two popping up for no other reason than to make more things happen, when they have nothing to do with the overall narrative. It's almost as if the producers are desperately trying to squeeze a trilogy out of a story that isn't really made for it, and are stretching what story they do have to breaking point in the process.
- Too Much Story: Conversely to the above, the first movie may have been made under circumstances that forced the producers to be more restrained in their goals for the first installment. The sudden prospect of a pair of guaranteed sequels may see the writers get self-indulgent and include everything in parts two and three regardless of coherence (maybe to get the ideas out of their system). The second and third movies thus become a clogged, confusing mess with a lot of excess fat.
- Pacing: Sometimes the second part consists almost entirely of exposition and the third part consists almost entirely of climax, so the former feels too talky and the latter ends up being all explosions.
- Pandering: The makers may decide to pander to the fan-base with the second and third movies, often at the expense of locking out the wider audience. This also tends to result in Flanderization, with the original plots and characterisation gradually reduced to cliches and stereotypes.
Analysis / Two-Part Trilogy
The nature of Two Part Trilogies lend itself to certain qualities that are produced in the writing of the story, and thus make it particularly susceptible to Sequelitis. It is certainly not a guaranteed issue, but such problems can include: