Credit: Ron Tom/ ABC

We'd already been looking forward to tonight's Grey's Anatomy Season 9, Episode 20: "She's Killing Me" (April 4),  but a new spoiler-y tweet from showrunner Shonda Rhimes has upped our excitement factor exponentially.

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"Last two minutes of tonight's [Grey's Anatomy]?" Shonda tweeted earlier today. "Change EVERYTHING for one of our characters..."

Whoa. Whoa! What do you think that's all about?

We have two theories. One is that the character in question is Meredith (Ellen Pompeo). In this sneak peek, Mer learns she has certain genetic markers for Alzheimer's. Maybe in the last two minutes she learns more specifics — good news or bad — that could change "everything" for her.

Our second guess is that this tweet is related to the plotline where, according to the official synopsis, "multiple pre-op patients develop infections, causing one doctor to wonder if she is at fault." Perhaps said doctor finds out she is at fault at the end of the episode. Depending what her mistake was, it could potentially be career-ending.

Of course, knowing Shonda Rhimes, it'll likely be something we could never predict, so share your theories in the comments below!

For more Grey’s spoilers, click here.

Catch the next new episode of Grey’s Anatomy on Thursday, April 4, 2013, at 9 p.m. ET/PT on ABC.

Source: @shondarhimes

Rebecca Martin is an editor at Wetpaint Entertainment. Follow her on Twitter @BeccaDMartin.