Justice League Unlimited Episode 5 - This Little Piggy
The centuries-old enchantress Circe transforms Wonder Woman into a pig as revenge against Diana's mother. Batman and Zatanna work together to return her to normal, while B'wana Beast attempts to find the "Wonder Pig" before she's butchered at a slaughterhouse. It contains the famous scene of Batman singing the jazz standard "Am I Blue?" to a nightclub audience.
In this episode Batman confesses that there is something between him and Wonder Woman. Throughout the entire episode it is very visible that Batman has feelings for Wonder Woman, and that she feels the same. This episode features the singing of actress/singer Rachel York, who performs Lulu's Back In Town by Al Dubin and Harry Warren.