I'm not sure how long The Great Blondie Crossover is going to last. The strip turns 75 on September 8 but today's strip looks like the big celebration. So this may be it.
Not a lot of Blondie activity in other strips today. Hagar the Horrible is about the anniversary, as is Bizarro. Other than that, the only other reference I've found is a tiny banner in Buckles.
Okay, people…there must be one or two I missed.