Hank Ketchum's seminal comic strip, Dennis the Menace, had made his television animation debut on Curiosity Shop in 1971 while his live-action series was in syndication. 10 years later, he had his first primetime special.
Mayday For Mother has a 1980 copyright, but was completed a year later after DePatie-Freleng had been purchased by Marvel and rechristened Marvel Productions. The Marvel staff finished the job, but chose not to take credit, so this would technically be the last DFE release.
The plot is a simple one. Reminded by a television broadcast of Mother's Day, Dennis Mitchell resolves to try to find a decent gift for his mother. The program features Kathy Garver (ex-Family Affair) as Alice, Dennis' mom, a few months before Garver was cast as Firestar in Marvel Productions' 1st official release, Spider-Man & His Amazing Friends.