The Calvin and Hobbes Wiki
Screenshot 2017-03-08-09-00-57-084

Calvin once dressed as a helmeted super hero in a single weekday strip. Calvin's mother asked him what was up today, to which Calvin replied, saying that nothing had happened yet, but if anything did happen, (by golly) he would be ready for it.

Calvin's mother thought that she needed a suit similar to Calvin's.

It also appears that this helmet is the same one used in the cover story of Yukon Ho! but with the visor flipped down.