This one's ki d of out there, but Bradley James for Barry Allen. I'm pretty sure he can do a good American accent and he can do comedy and snarky comebacks, much like Barry but also be the CSI and intelligent side of Barry.
Harry Potter was saved by a mother's love more than once. Harry may not of had his mother but he had a lot of comfort from mother like figures. Whenever Harry needed comfort it was always from a mother figure.