April O'Neil is currently the only human ally of the Ninja Turtles. Donatello is in love with her. Her real name is April Liliana Mari O'Neil
April is very adventurous. She likes to come on some of the Ninja Turtle's missions. Splinter is training her to be a female ninja so that when she goes with the Ninja Turtles she will be able to defend herself. It is also proven that she is determined to kick butt when Splinter first mentioned to April about being a female ninja
Leonardo- They are good friends and show respect for each other and Leo is the only one who is the most determined to get April's dad back from the Kraang. Leo also seems protective of April and tries to stop her when she tries to do anything dangerous like spying on the Kraang.
Raphael- They dont interact much but they are still friends
Donatello- April is his love interest but she doesnt seem aware of it. Donnie tries his best to make her aware but throws it away afraid to get rejected. On a second note they are still good friends and try to help each other out
Michelangelo- He is like her little brother always telling jokes and pulling pranks April is Mikey's only human friend but he doesnt seem much aware when he stated the fact that she had to like them because they saved her. April seems a little annoyed by this but they are still good friends