The tag mikes-sister appears in these 3 comics:

• 52: (12/15/2012) Big Wheel (Tags: mike, mikes-sister, mikes-mother, young-mike)
• 53: (12/22/2012) Schrödinger's Tree (Tags: mike, cat, mikes-sister)
• 79: (06/22/2013) Attack Cat (Tags: mike, mikes-mother, cat, mikes-sister, time-machine)