Camille Guaty as Megan O'Brien (season 1–2) is Walter's sister and Sylvester's wife, who had multiple sclerosis, a condition that Walter sought to "fix" to repay the favor of her always being there throughout his childhood.
Camille Guaty kao Megan O'Brien (1. i 2. sezona), Walterova sestra oboljela od multiple skleroze, bolest za koju je Walter pokušavao pronaći "rješenje", kao način na koji bi joj se odužio za njenu stalnu podršku kroz njegovo djetinjstvo.