Shades of Sybil! When Clark Kent is exposed to Red K after attending a ventriliquism performance, he becomes schizophrenic and builds a Superboy dummy. He then proceeds to berate and slap said dummy around, to the astonishment of his foster parents! This Silver Age gem is from Superboy # 122 ( July 1965, DC). Story by Leo Dorfman, art by George Papp.
The earliest adventures of the Smallville Sensation have just been collected in hardcover form in The Adventures of Superboy. The book reprints Superboy tales from More Fun Comics #101-107 and Adventure Comics #103-121.