As we have seen with episodes such as “Mr. Pigeon 72″ and “Optigami”, several season 4 episodes appear to be paying homage to earlier episodes. I think that this pattern will occur with “Sentibubbler”, in a very specific way.
To explain I want to first bring to attention the title card for the episode “Mr. Pigeon 72″:
In the the pictures around Marinette, it is seen that Adrien is wearing the scarf she made for him in most of the pictures. If you recall the episode in which she made him this was “The Bubbler”.
Being as how these are new pictures, it is no coincidence that these appear in this episode, the very same episode that features a new umbrella scene (with a possible development of Adrien’s feelings for Marinette). The pictures of Adrien wearing this very scarf hold some form of symbolism. Now this symbolism could just be that Marinette has rediscovered her love for Adrien and so the pictures around her show a previous example of her love for him. However, I have a different theory.
My theory is that this title card is a hint to the fact that in this season Adrien will discover that in was Marinette and not his father who made him the scarf. I think that this plot point will come full circle and this reveal will happen in “Sentibubbler”, which will further cement the change in the love square.
Again, this is just my theory, I could be (and probably am) very wrong.