If there were no malicious or uninformed people this would be great. Unfortunately there are, and programs like this are dangerous in the wrong hands. I'm sure no paying member of DonationCoder would misuse this, but others will.
This blurs the line between harmless and harmful. A non-computer-savvy person might receive a Dr. Windows message, only to be told it's a joke. The next message might be malicious and the user might take the wrong action.
I know, I know, it's only silly fun. But perhaps DonationCoders don't think about the majority of computer users. I teach computing skills to a group of senior citizens, and they would be terrified by even the penguin joke. If little Joey decided to pull a prank on Gramps, who knows?