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.
YMMV: Bad Days
Big Lipped Alligator Moment: A few of Stan Lee's cameos, such in Star Trek where he's teleported into the transporter room, dressed in a tuxedo and singing "Hello, My Baby!", or in the second Iron Man episode, where he's sitting on a tiny planet in outer space.
Captain America somehow pulls out and blows a conch shell when Bruce Banner Hulks out in the bowling alley.
Ear Worm: The music that plays during the opening credits will become infectious the more frequently you watch, especially since cartoons from season two play it at both the beginning and the end.