>>149797308
Rebecca Sugar as Calliope
Alex Hirsch as Caliborn

Consider:
Rebecca as Calliope
Alex as Caliborn
Rebecca has an incredibly sweet and soft voice, just gotta put on an intentionally fake british accent
Alex can do the Grunkle Stan voice for Lord English
That way we get Vivzie + Toby + Homestuck + GF + SU, the ultimate fandom combo