Who is Dr. Whale (David Anders)? It's the question on every Once Upon a Time fan's mind. Is he Dr. Frankenstein? Peter Pan? The theories are endless and the anticipation is building.

To help you try to puzzle it out, we've collected the juiciest Whale-related spoilers right here.

Read spoilers at your own risk! For more on Wetpaint Entertainment's philosophy on spoilers, click here.

We find out the truth in Episode 5: Season 2, Episode 5, appropriately titled "The Doctor," will reveal all. David Anders has teased that the episode will "knock [our] socks off." The synopsis for the episode doesn't give us many more clues, though.

Whale and Regina: It sounds like Whale will have an intense backstory with Regina (Lana Parrilla) that we'll learn about in Episode 5.

Blood? Injured arm? Cooler? Huh? Some dramatic behind-the-scenes pics show Whale taking a cooler to (from?) Mr. Gold/Rumplestiltskin's (Robert Carlyle) shop. There's blood on his shirt, and it looks like there's something up with his arm — David Anders is wearing a green-screen armband and keeps the arm hidden in many photos.

We'll never guess: David Anders claims fans will never guess who he is. Do you believe him?

Clues from the start: Want to try to prove David wrong? Well, the writers have been planting clues since Day One. Time to break out the Season 1 DVDs!

Catch the next new episode of Once Upon a Time on Sunday, October 7 at 8 p.m. ET/PT on ABC.

Rebecca Martin is an editor at Wetpaint Entertainment. Follow her on Twitter @BeccaMartin47.

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