Benedict Cumberbatch
Benedict Cumberbatch became a major star after appearing as a modern-day Sherlock HolmesGetty

Benedict Cumberbatch is working on a super-secret project for BBC One and BBC Two and looks like fans are really hoping it could be a Doctor Who/Sherlock crossover.

The news that Benedict Cumberbatch is filming "something special" and highly secretive for BBC One and BBC Two is sure to make his fan base go into overdrive, states a Mirror report.

BBC One shared two mysterious snaps of the star on its Facebook page and wrote: "Benedict Cumberbatch filming something special for BBC One and BBC Two. More details soon…"

Several users started speculating what the "special" could be. Here's what some of the hopeful ones posted:

"Doctor who cross over" – Kerval Soni

"If it's for children in need please be a sherlock/doctor crossover" – Emma O' Mahony

"Based on the time of year it must be for children in need… please be Doctor Sherlock crossover." - Rae Ann McCardell

However, here is what the Mirror stated about the secret, along with other possibilities: "Sherlock isn't due to investigate another mystery until next Christmas and he looks vastly different to his regal role as Richard III in upcoming BBC Two film The Hollow Crown."