For completion, since the comments to the previos entry mentioned a couple ones that I missed.
Action Comics #319 (1964)
written by unknown
pencils by Jim Mooney
Thanks to Patrick Smith for highlighting I missed this Silver Age cameo!
It’s in a Supergirl story where she has to expose a girl who framed her as being a cheat.
The solution is thanks to Shrinking Violet, who her father knows.
Supergirl just probably told him, sure, but then why is he explaining her powers? Unless she told him but NOT her mother?
Not really sure Supergirl needed her for something this simple.
Shrinking Violet is lying. Very little interesting stuff happens to Supergirl when she goes to college.
DC Sampler #1 (1983)
by Paul Levitz & Keith Giffen
An amusing ad for the Legion.
Showcasing its rising popularity, since apparently readership had increased by 50,000 copies.
Each panel is a reference to the classic logo of another DC series. That’s neat!
DC Challenge #10 (1986)
by Dan Mishkin & Curt Swan
A cameo from Shadow Lass’s ancestor. Which makes me wonder: why did Superman recruit the ancestor instead of traveling to the future to recruit Shadow Lass?
Interesting letters:
Ambush Bug #1 (1985)
by Keith Giffen
A letter by Ferro Lad of all people.
I have another one: Action #307. In “Supergirl’s Wedding Day”, Saturn Girl cameos as a surprise bridal stand-in.