Bizarro is brought to you today by Rodents To Be Pitied.
When I was young, I never bought the idea that people in animal costumes were actually the character they were pretending to be. I sensed they were regular people in giant costumes and was appropriately frightened of them. My mother would take us to get our picture taken with the Easter Bunny and I'd cry.
This cartoon isn't about the Easter Bunny, but it goes to a pretty strange place with no apparent explanation. I like this kind of humor, that which portrays an extraordinary moment in time not easily explained. Fans of this sort of thing don't need an explanation, it's just funny that this poor sap is in a bunny costume and talking about his hard luck and country western songs. Others with more literal minds, may think the drunken bum is imagining it. That's fine, too.
The real answer is that the upside-down bird under the bench is the world's foremost avifaunal performance artist and he has orchestrated the scene for the benefit of passers by.