An interesting fan theory from How I Met Your Mother suggested that Ted Mosby

was suffering from Alzheimer's disease based on his narration.

One of the most popular fan theories from How I Met Your Mother suggested that Ted Mosby

from the future timeline was suffering from Alzheimer's disease.

The character was played by Josh Radnor for the duration of the sitcom, which aired from 2005 to 2014. Though Ted narrated the series, Bob Saget served as the voice of Future Ted from the 2030 timeline.

Here's why the theory caught fire and why some viewers still believe it, despite the series finale's revelations.

How I Met Your Mother was set in the present-day in the eyes of viewers but to Ted,

the stories being told were from the past. It was the year 2030 and Ted was telling his kids, Penny and Luke, the story about how he met their mother.

The story, explained through narration, was the driving force behind the sitcom as it followed the life of Ted and his friends from their mid-twenties to their early thirties.

As the series went on, Ted got closer and closer to meeting the "Mother" before the character became a focus in the ninth and final season.

With Future Ted steering the events of How I Met Your Mother through his storytelling and recollections,

any continuity errors or out-of-order details were deemed his fault.

Rather than blame the writers, many fans theorized that Future Ted was suffering from early signs of Alzheimer's disease, a disorder that affects the brain when it comes to critical thinking and memory.

Rather than just sharing a story about how he met his wife, some viewers thought Ted was sharing the details before dementia truly set in.

The theory caught even more attention in the season 8 episode, "The Time Travelers", because Future Ted wished he could have an extra 45 days with his wife.

This confirmed viewers' worries that something bad was going to happen to the Mother, Ted, or both.

The Evidence Supporting (& Debunking) HIMYM's Alzheimer's Theory

The main evidence surrounding Ted having Alzheimer's disease was the fact that the character

was shown to be an unreliable narrator.

He often mixed up certain dates and left out important details when telling the story to his children.

Ted also seemed to fill in certain plot gaps before coming back later with changes.

Even after the series finale aired with no hint that Ted was suffering from any kind of illness, some viewers were still convinced that the future version of the character had Alzheimer's.

More than likely, Ted became an unreliable narrator because he was telling a very long story in 2030,

decades after everything happened.

A story that intricate would make anyone forget certain details.

There were also no other signs of Ted having Alzheimer's disease when it came to his behavior.

How I Met Your Mother ended the series with the revelation that the Mother, Tracy, passed away six years prior, so there would be no way the writers would also give Ted a debilitating illness.

The conclusion was depressing enough for most viewers, and though the Alzheimer's theory is interesting, it can mostly be debunked.