You need a scorecard to keep track of all the personnel shakeups underway on your favorite returning shows (hey, such a scorecard exists!). But there’s one slide conspicuously missing from TVLine’s comprehensive Fall TV Cast Changes roundup — and with good reason. You see, this particular piece of casting news is intended to be a spit-take-worthy shock to end all spit-take-worthy shocks. [UPDATE: BLIND ITEM REVEALED!]

According to sources, a returning series on one of the Big 5 networks is getting ready to pull off what will likely go down as one of the coolest, most surprising casting stunts of the year. The onscreen twist — which was shot earlier this month under a Star Wars-level veil of secrecy — is set to air during the show’s season premiere.

Prediction: The show — and [Spoiler]’s name — will be trending on Twitter before the closing credits roll.

Normally, we’d tell you to hit the comments with your best guesses, but we’ve given you so little to go on, it probably makes more sense for you to just share with us your ultimate stunt casting fantasy.