We've examined this phenomenon before: the casual way in which Batman and Robin would encounter celebrity characters from other shows (sometimes from other networks).
Today, we watch as they meet Lurch from The Addams Family. I'm pretty sure Addams Family had been canceled before this episode aired, so this is an especially poignant moment.
For added entertainment, enjoy the video comments that speculate that the rest of the Addams Family is inside with Lurch, and how Batman should have mistaken Lurch for Solomon Grundy.