Ice Cream Old Man

The ice cream man appeared on the 5th episode of the second season of the Toaru Kagaku no Railgun anime series and on the 22nd chapter of the Toaru Kagaku no Railgun manga series.

Sisters Arc
The ice cream man appeared while Mikoto and Misaka 9982 were "fighting". He  decided to intervene, not wanting twins to go on arguments like those, and gives them a cone of ice cream each, telling the two to get along before leaving; a choco-mint for Mikoto and a strawberry-vanilla for Misaka 9982.

Quotes
 "If a married couple divorce, they become total strangers, but the bond between siblings lasts a lifetime."—to Mikoto and Misaka 9982.