That's "seceding" eyebrows (not succeeding as you've typed) - as in breaking away - a joke aimed at the British audience since the Scots are about to have a referendum on whether or not to become independent of Britain again.

I had no clue about Eleven's cameo. At the time, half of me thought it was lovely, the other half of me was irritated, but having re-watched the ep, I'm wholly irritated as it wasn't needed.