It's not an anomaly, a conundrum, or a fallacy, it's a PARADOX! For time travel stories, my impression is that despite the different names, they all involve inconsistent causal loops, unless the multiverse is introduced. The difficult part of time travel paradoxes is to think out of all of the possible ramifications due to the circular nature of events. Spoilers for: 12 Monkey (movie), STNG: All Good Things, Interstellar, Back To The Future In the Back to the Future movie, the concept is easy to understand that if McFly does not get his parents together, he will cease to exist, by virtue of a fading photograph, which as I recall ,a photo was used in both the 1st and 3rd movies. However what the movie does not address is all of the peoples' lives he has effected by interacting with them, other than the benefit to his own family. Maybe he inspired the "soda jerk" to become mayor. This is an altered timeline. Best not to think about all the changes that occured to Marty by virtue of the altered time line, and how he would mesh returning back to his now changed former life. In 12 Monkeys, a character Cole is sent back in time to look for an organization called the The Army of The 12 Monkeys, an organization believed to be responsible for the outbreak of a deadly disease that wipes out most of humanity. However he arrives earlier than the target date, inquires, and inspires an inmate at a mental institution, which starts a chain of events. This would be a bootstrap paradox. In Interstellar, a character from the future leaves clues in the past so the path forward can be established. Future Cooper leaves hints to his daughter in the book shelf, her ghosts, which helps himself move forward. However my favorite paradox occurred in Star Trek Next Generation series final All Good Things where Capt Piccard finds himself traveling through time, jumping back and forth in his life. This is another test perpetrated by Q. In the past, he becomes aware of a temporal anomaly close to the Devron System in the Neutral Zone and discovers that by virtue of being a temporal anomaly, it is moving backwards in time, growing as it moves backwards. His retired self vowes to cajole his friends into transporting him to the Devron System to look for it at an earlier state, searching by means of deploying a reverse tachyon beam. The cause of the paradox is that he is the one who causes its creation by looking for it! Jumangi- A favorite movie, no time travel, but creates a time line that is later erased when the game concludes. No paradox, simple to understand. One of the earliest time travel stories I am aware of is The Sound of Thunder, a 1952 Ray Bradbury story which is the origin for the term "butterfly effect", where a time traveler steps on a butterfly and the future is changed. Looper- the worst time travel movie I've seen if the goal is to all most understand why things happened the way they did. Nine Problems With Looper. Some of these links have contrary ideas regarding time travel. A TimeTravel Website Rules of Time Travel@ Wikipedia. 1. Single fixed history, which is self-consistent and unchangeable. In this version, everything happens on a single timeline which does not contradict itself and cannot interact with anything potentially existing outside of it. 2. History is flexible and is subject to change (Plastic Time). Events can be altered, but there are different variations of this branch from time is easy to change (Back To The Future) to major changes are hard to achieve. 3. Alternate timelines. In this version of time travel, there are multiple coexisting alternate histories, so that when the traveler goes back in time, he/she ends up in a new timeline where historical events can differ from the timeline he/she came from, but his/her original timeline does not cease to exist (this means the grandfather paradox can be avoided since even if the time traveler's gran Three types of Time Travel- Fixed Timeline, Dynamic Timeline, and Multiverse. -Fixed Timeline- Even when parties travel back in time... the future they left cannot be changed. All events remain as fixed poinst in time. The actions of the traveler in the past have already become part of hisotry. This is known as the Novikov Self-Consistency Principle. For Example, say you travel back in time in order to kill Adolf Hitler as a baby in order to prvent WWII. You replace him with a orphaned baby, so that the family will not notice. You trave back to the Future, and the replaced baby grows up to becom Adolf Hitler Himself (The Terminator, Harry Potter 3, 12 Monkeys). -Dynamic Timeline- Altered events in the past have definite impact on the present. For example: If you travel back in time and kill your Grandfather... you also prevent your own birth, and your eventual trip back in time, in turn, your Grandfather is never killed, and you are born again, only to go back in time and kill Your Grandfather anyway. A Paradox as seen in Back to the Future. Confusing? YES. -Alternate Timelines- With an infinite number of parallel universes, traveling into the past causes a new divergent timeline from the first. Because of this, the traveler can do anything with impunity, and only the new timeline will be effected. For example, if you kill all your grandparents, nothing happens. There is no paradox, you have simply created a new timeline in which you will not exit, but the original timeline is unaffected. However, you cannot return to the original timeline. (But I assume you are still existing in the new reality you created, you just magically appeared there?) Top Five Philosophical and Science Fiction Paradoxes Grandfather Bootstrap Paradox of Value Dream Argument Paradox of Hedonism? Bootstrap Paradox: Grandfather Paradox- Inconsistent Causal Loop.