Been thinking about fusions lately-
Tedd has Edd's radioactive powers and Tom's demon blood, a bad mix that screams villain, but he has a good heart. A cuddly boy, always either tired or drunk on coke vodkas.
Method:
Two eyes = both Edd and Tom see situations similarly
Three arms = both Edd and Tom would react in different ways, but only due to Tom's apathy
Two mouths = both Tom and Edd would verbally react in different ways