Complex sentence: When one of the puppies stands on his hind legs, Mr. Burns picks him as his favorite of the bunch, claiming that the puppy reminds him of actor Rory Calhoun, and names him "Little Monty".
Split into simpler sentences: When one of the puppies stands on his hind legs, Mr. Burns picks him as his favorite of the bunch. Burns inexplicably claims that the puppy reminds him of actor Rory Calhoun, and names him "Little Monty".