The end has finally approached for How I Met Your Mother, and as fans prepare to say goodbye to the show, a popular theory on how the show will end has once again resurfaced.

The Mother Dies And Ted Rekindles The Flame With Robin?

Fans have speculated for some time that the titular mother character (played by Cristin Milioti) would die in the series finale episode of the show, prompting a perfect reason for Ted to be telling his children the story of their mother.

Though Milioti herself has dismissed the theories as "insane," they have been given new life once again, thanks to the official release of the series finale's guest stars.

Ted Has Alzheimer's Theory

According to International Business Times, the official list of guest stars featured in the series finale will not only include the more grown-up versions of Ted's kids, Penny (Lyndsey Fonseca) and Luke (David Henrie), but also Bernice (Judith Drake), Ranjit (Marshall Manesh), Joe Nieves (Carl) and Nurse (Saudia Rashed) among others.

The inclusion of a nurse character on the episode has caused fans to speculate that the mother character will in fact be revealed to be terminally ill, and will later die in the episode.

The official promo video for the series finale episode has also resulted in an increased fervor of speculation about the mother's death as well.

"You've laughed with them, you've cried with them...now it's time to say goodbye," the promo teased. "And let them surprise you, one last time."

As the promo leads into the allusion of a surprise, fans see a clip of Robin looking down from a cliff and seeing Ted standing on a beach. If the theory about the mother's death does pan out, there could be a twist which sees the couple reuniting, despite her recently going through with her wedding to Barney.

The How I Met Your Mother series finale airs March 31 at 8 p.m. on CBS.