Slightly off-topic admittedly: from the flip side of this question, an act of trolling which fooled all the key academics for some 40 years was the Piltdown Man Hoax. Discovered by Charles Dawson in 1912 he was initially regarded as a vital palaeoanthropological find, was heavily studied and was believed to be providing important clues in the evolutionary link between apes and humans. Eventually the hoax fell apart and London's Natural History Museum did a feature piece to mark the 100th anniversary of the "discovery".

One explanation for the Tecaxic-Calixtlahuaca head, an apparently Roman artefact found in Brazil, is that it was planted as a practical joke during an archaeological dig.

There's a term among archaeologists and the like, ooparts or "Out of Place Artifacts."

However, as a caveat, due to their curious nature, and some of their (preposterous) implications, they tend to be the center of a great deal of pop-history/parlor curiosity type studies.

One such oopart though would be the antikythera mechanism

A good portion of these items are likely fairly mundane items that have been wildly interpreted, for example the "Baghdad batteries" (Secondary analysis of Baghdad batteries, but with citations).

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, questions of this type can be directed to more appropriate subreddits, such as /r/history or /r/askhistory.