Is this a mulberry? It looks to me like a plant sport which is a variation arising from a single plant that differs genetically from the parent plant, it is essentially a mutation that manifests as a noticeable change in a plant’s characteristics, it can sometimes happen when the cellular structure has been messed with (say cutting off a limb) and the dormant buds grow and divide in differing ways giving the variation in the leaf characteristics. It’s just a guess though.