Simple:
* The movie's plot was so far-fetched that it was hard to believe.
* His explanation for being late was far-fetched and unconvincing.
With context:
* The conspiracy theory was so far-fetched, it seemed like something out of a comic book.
* Even the most far-fetched ideas can sometimes lead to amazing discoveries.
* Her story about meeting a unicorn was so far-fetched, no one believed her.
Figurative:
* The detective's theory was so far-fetched, it stretched the limits of imagination.
* His explanation was so far-fetched, it felt like he was reaching for the stars.
Remember, "far-fetched" implies something that is highly improbable, unbelievable, or outlandish.