This comic has what is possibly the best first panel of any comic I ever wrote.
A few weeks after this comic ran, a nationally syndicated comic did a strip based on the same idea. A few readers pointed it out, but I chose not to make a big deal out of it. I’ve been in the “trying desperately to think of something funny to say” business long enough to know that this stuff happens.
Right now, all around the world, there are thousands of comedians, writers, and cartoonists trying their hardest to come up with an original funny idea. It’s inevitable that two people will get a similar idea around the same time occasionally. Plagiarism is, of course, completely unacceptable, but the syndicated cartoonist in this case does original work, and their execution of the idea was different enough that I was happy to give them the benefit of the doubt.
I may seem overly trusting to you, but I’ve been on the opposite side of this problem more than once. A couple of times when I was a comedian, I had people (one of whom I had never heard of, and another whose writing I had ZERO respect for) accuse me of stealing from them. I also once did a comic about the fact that my middle name is Oscar, and I ended up doing a joke that was very similar to a preexisting comic from the excellent webcomic Perry Bible Fellowship.
Heck, just a couple of weeks ago, I wrote a commentary on this very website where I discussed my attitude toward Millennials, and a couple of days later, after I’d written it but before it posted, the author John Scalzi wrote a very similar opinion on his blog.
These things happen. You just have to make sure they aren’t happening deliberately.