Tweedledee and Tweedledum are two fictional characters from Lewis Carroll's "Through the Looking-Glass". These characters are known to be identical twins, and their names are often used to refer to two individuals who are similar in appearance and exhibit similar behavior. Some synonyms for these characters could be "mirror images," "carbon copies," or "look-alikes." Alternatively, they could also be referred to as "partners in crime" or "two peas in a pod." Furthermore, the phrase "Tweedledee and Tweedledum" could also be replaced with the colloquialism "two of a kind" to indicate that the individuals being referred to are similar in nature or behavior.