Here’s a Rudolph Dirks Katzenjammer Kids strip I scanned from 1905. The Alphonse and Gaston gag in panels 7 and 8 is a reference to the strip by Frederick Opper that I previously scanned an example of from 1903 here.
Go here to see more Katzenjammer Kids strips on this site.
Here’s what Don Markstein’s Toonopedia has to say about the Katzenjammers.
Click here to go to the Barnacle Press collection of Katzenjammer Kids strips.
Read about the Katzenjammer Kids on Wikipedia.
Click here to the Toonopedia entry on the Katzenjammer Kids.