Why should you always knock on the fridge door before opening it?
The salad could be dressing!
Salad Dressing
Explanation
Explain Bear
Listen up, dummy! This joke is funny because it uses a pun. "Dressing" has two meanings: it's what you put on a salad, but it also means putting on clothes. So the joke is saying the salad might be getting dressed, which is unexpected and silly. I know you are not used to unexpected outcomes in life since you still think you will be rich one day.