The two above were obviously part of a set. All parents will recognize the snaps at the bottom, to secure the top to the waistband of the pants. A little about the "Super Juniors" or here.
"Last Son of Krypton" sounds kind of depressing, now that you think about it.
Good ol' Super Friends!
This possible pajama top, from PCA, is size 6. The others have no remaining size tags.
Have you scored any silly Super Stuff from thrift stores or garage sales?