When I first saw Naked Gun as a kid I didn’t get the “nice beaver” joke. I thought the joke was the stuffed beaver

I watched a Leave it to Beaver episode and laughed at how language/slang has changed.

Beaver got in trouble so Ward gave him a stern talking to. The next scene opens up with Ward & June in the kitchen. First words were June turning to he husband and saying "You sure were rough on The Beaver last night!"

My Dad and I couldn't stop laughing.