Ok, how about this for an idea. We take it in turns to post a favourite (British spelling) comic cover every day. This went really well on the comic fan website that I used to frequent. What we tried to do was find a theme or subject and follow that, until we all got bored with that theme. I'd like to propose a theme of letters of the alphabet. So, for the remainder of October (only 5 days) and all of November, we post comic cover pictures associated with the letter "A". Then in December, we post covers pertaining to the letter "B". The association to the letter can be as tenuous as you want it to be. For example I could post a cover from "Adventure Comics" or "Amazing Spider Man". However Spider Man covers can also be posted when we're on the letter "S". Adventure Comic covers could also be posted when we're on the letter "L" if they depict the Legion of Super Heroes. So, no real hard, fast rules - in fact the cleverer the interpretation of the letter, the better, as far as I'm concerned.
And it's not written in stone that we have to post a cover every day. There may be some days when no cover gets posted. There's nothing wrong with this, it just demonstrates that we all have lives to lead.
If everyone's in agreement I'd like to kick this off with one of my favourite Action Comic covers, from January 1967. Curt Swan really excelled himself here.
I can't speak to Fritzi. My recollection is John Stanley did Nancy and Sluggo stories.
Sometimes the star-switches were creator-driven. Mike Nomad was introduced into Steve Roper because William Overgard couldn't sell his Mike Nomad strip.