These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
And You Thought It Would Fail: Before its release, there'd already been three Overnight Age-Up comedies made between 1987 and 1988: Like Father, Like Son, 18 Again! and Vice Versa (not to mention the Italian film Da grande, which was this film's direct inspiration), so many expected this film to tank and be forgotten. Instead, Big became the highest-grossing and most highly-praised film of the bunch.
Better on DVD: The extended cut elaborates further regarding Josh's wish to be big.
At Josh's apartment, he has a model of a Saturn V rocket from the Apollo space program. Several years later, Tom Hanks would star in Apollo 13.
Overlapping with Technology Marches On, Billy scoffing at Josh's interest in computer work is pretty funny now that computer skills are a very helpful thing to have.
The movie actually seems to have been aware of this, as it's his computer skills that get Josh a job.
Josh's idea for an electronic comic may also count as Defictionalization or Life Imitates Art. While electronic texts existed in the late 1980s, e-books didn't start out-selling print books until the 2010s.