Mayhem hadn't noticed the boy at first intill she bumped into him. She apologized shortly, "Sorry!" The boy gave her an odd look, and she right back,
"Have we met before...?"
That was all it took (plus the t-shirt) for Mayhem to figure it out. She squealed and gave a little jump, "HALO! Omigod, its you!!!" and she hugged Halo in greeting.