BornFromHell08
(Takes place in season four)
As a fandom, I feel we don't talk about the relationship between Fugitoid and Donatello much. We all see the differences in how Donnie's relationship is between Splinter and The Fugitoid.
Donatello's relationship with Splinter is a blend of respect and his way of having a peaceful soul.
With his relationship with Fugitoid, he seemed more calm than tense, getting the advice he needed and seemed more laid back instead himself shuting himself in his lab or room.
So with all the evidence needed, I hope you enjoy Father Figure. :)