The strange poop is cecotrophs, rabbits normally eat them as they come out of the anus. Rabbits are designed to digest very hard to digest food like grasses so they pull nutrients out into the cecum and produce cecotrophs which are re-ingested to maximize nutrient intake.
Occasionally you will find some that are not eaten, but if it becomes a regular occurrence, then something is wrong with the diet usually. Most cases it is too much protein or carbs in the diet causing excess cecals.
But if it is just one every once and a while, nothing to worry about.
Oh, mothers will also leave some around for her babies to eat as their digestive system matures.