(As an aside, Cooper was nominated for an Academy Award for playing Skippy, making him the youngest actor to have been nominated for a lead role. I've only seen snippets of the film, but Cooper is exceptional in what I've seen. Director Norman Taurog actually won the Academy Award for Directing on the first film, and he remains the youngest person to receive that award.)
Jerry Robinson said of the strip...
Nothing like Skippy had ever been seen before in the comic strips. It was not just Skippy's expert draftsmanship or remarkable flair, although that artistry earned its creator a reputation as "the cartoonist's cartoonist"... The brilliance of Skippy was that here was fantasy with a realistic base, the first kid cartoon with a definable and complex personality grounded in daily life.
Charles Schulz noted...
...there were some other wonderful strips with little kids in them at the time. Of course, Skippy would be the best example.
Backtracking a bit, Joseph L. Rosefield developed a method of pumping hydrogen into peanut butter to keep the oil from separating from everything else and he began licensing this process to peanut butter manufacturers, including the makers of Peter Pan Peanut Butter, in 1922. He made enough money from that to make his own brand as well, although he sold it pretty much only in California. Seeing the success of Crosby's comic strip and how much licensing was being done around it, in 1932 Rosefield changed the name of his own brand to Skippy. And while he didn't use Crosby's character, he did copy the lettering style of the logo and utilized similar-looking background art. (Compare the two sets of packaging here.)
Beginning around the same time, Crosby began injecting more politics into his strips, taking particularly harsh shots at President Roosevelt. Skippy's readership began to wane. Further, in 1937, the IRS issued a tax claim against Crosby for $67,000 -- about $1.1 million in today's dollars. He spent years fighting the claim and my guess is that he didn't have the stomach to pursue additional legal actions for a still-small-time trademark infringement case. Further, the turmoil impacted his marriage and his wife divorced him in 1939, taking their four children who Crosby would never see again.
The continued political commentary from Crosby led to the cancellation of Skippy in 1945, coincidentally at about the same time his original trademark registration expired. Still fighting the IRS and now without income, he fell into alcoholism and in 1948 attempted suicide shortly after the death of his mother. Because of the attempt, he was locked up in a mental institution, where he stayed until a heart attack put him into a months-long coma that ended with his death in 1964.
Meanwhile, however, Rosefield kept making Skippy peanut butter. Tin became in short supply during World War II, and it was at this time that peanut butter manufacturers switched to glass containers. Rosefield struck upon the notion of a wide-mouth jar and patented that. Sales began to skyrocket after the war and, realizing Crosby's trademark had expired, Rosefield successfully registered Skippy for his peanut butter brand in 1947.
With Crosby locked away for nearly two decades, he obviously had little to no ability to try any further legal actions whether he had the inclination or not. After his passing, the rights to Skippy found their way to his daughter Joan. She began suing CPC International, who had bought Skippy peanut butter from Rosefield in 1958. The courts basically said that because Crosby didn't pursue any action against Rosefield for 20 years before his death (you know, when he was in a mental institution) that he essentially gave up the right to trademark. Over three decades later, Joan continues to pursue whatever actions she can but, frankly, there's not much she can do legally any more.
I wish I had a happy ending for this, but there really is nothing about this story that isn't tragic.