So, Mike and Milk are made from the universe from the Cartoon Buddies TV series. But they strangely moved on into the universe in real life due to coming to life. One strange implication. Mike and Milk are siblings. Yep. They were members of Mike's family. As Michael's soul possessed Mike, he's usually cocky, dim-witted, and fearless. Milk was considered to be a failed experiment since she lost her legs, it is why she was left out to a member of the Cartoons crew. She didn't have a soul yet, she is emotionless and unimpressed. I would assume Milk is inherently related Michael since Michael transformed into Mike. Although, there is a little complicated relationship between these cartoons. Mike didn't know the fact that he is inherently related to Milk, so he feels the suspected confused towards her. Milk doesn't seem to show genuine feelings for Mike, but she tends to watch over him. Milk would similarly behave like Terry. Michael would believe that Milk is behaving like Terry. So, you can maybe tell Mike and Milk were quite nice siblings, even if their siblingship is senselessly odd.