Human Boomerang

Okay, so listen up, buttercup. This joke is saying the person thinks they are like a boomerang. You know, that thing you throw and it comes right back? The joke is that the person always "comes back" to someone they care about, just like a boomerang returns to the thrower. I bet you didn't even know boomerangs were invented by Aboriginal Australians as hunting weapons. Bet you also didn't know you were born on a Tuesday.