With the series finale of CBS' How I Met Your Mother just days away, fan theories have gone wild on how the series will wrap up its nine-year tale.

Mother's Death Theory Resurfaces Amid Series Finale Chatter?

Though the series creators and cast won't confirm or deny if the various fan theories are true, some things fans can expect in the special one-hour finale episode have spilled.

Back in a March 18 interview with TV Guide co-creator Craig Thomas hinted that a special guest star would return for the series finale, saying it would be a "fun, random one from the past," and now, with the official list of guest stars set to appear in the episode being released, it is clear which one he was referring to.

Ted Has Alzheimer's?

According to Hollywood Hills, the episode's guest stars will include: Judith Drake (Bernice), Marshall Manesh (Ranjit), Joe Nieves (Carl) Saudia Rashed (Nurse), Courtney Hope Turner (Girl), Brooke Lynn Howard (Sexy Girl #1), Justene Alpert (Sexy Girl #2), Alexandria Skaltsounis (Erin), Patrick Kang (22-year-old Guy), and Kerrigan Milker (Girl).

Fans of the show will remember that Bernice is the older woman Ted meets on the train platform in Farhampton, before he meets the titular mother character. Though future Ted has been telling the story of how he met the mother to his kids for nine years, what happens between Ted and Bernice on the train platform could prove to be extremely significant to the overall story.

When Ted first met Bernice on the train platform in the season 8 premiere, he began telling her the story of Robin and Barney's wedding, from the moment Robin asks to see him.

Though Ted has since let go of Robin and allowed himself to open up to other potential women, he could be telling Bernice the whole story of how he once loved Robin and despite letting her go, a part of him was still sad to see her marry his best friend.

Fans also know that while he and Bernice both sit on a bench at the station, the mother also arrives, and it is where she and Ted will meet for the first time. The character has been known throughout season 9 for dispensing valuable advice to the other characters, and could potentially overhear Ted's story, where she will interject with the final advice he needs to hear.

Watch a clip from the season 8 episode below.

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