Intertextuality is the relationship between two texts.
Three types of intertextuality are obligatory, optional, and accidental. Obligatory intertextuality is when the writer deliberately invokes an association to another text. Optional intertextuality is less impactful and not needed but will shift the effect of the text on a reader. Accidental is when the writer doesn't clearly connect the text, and the reader needs prior knowledge to get the reference.
The first one includes Boo from Monster's Inc. holding a Nemo toy. This is an accidental intertextuality because there is no intention of connecting the stories but the watcher has to use prior knowledge to recognize the toy.
The second one is Family Guy remaking the cover of the Star Wars movie. This is obligatory intertextuality and the writer deliberately connects the two because that's what the episode was about.
Finally, Pinocchio was shown in Shrek. This is most likely Accidental however it could have impact and be optional.