slap me upside the head and call me Larry Pinto

An exclamation reflecting a state of amused disorientation, often prompted by a surprising or unexpected event of a generally positive nature. Suggests being so delighted or amused that one cannot remember their own name.

"Well, slap me upside the head and call me Larry Pinto! Did you see that, Lou? That was the biggest pineapple I've ever seen!"