Napoleon Dynamite is like if Superbad was nothing but that scene of Michael Cera singing "These Eyes" by The Guess Who. Just 100% cringe, awkward interactions between the main characters. Like an inside joke that literally nobody is meant to get, even the people "in" on the joke.
Honorable mentions: Nacho Libre (similar in its randomness), Wayne's World (a classic) and Road Trip (similar to Superbad in its frat humor).
Wet hot American summer have me both Superbad and Napoleon Dynamite vibes. It is likewise unexpectedly heartfelt, while being satirical about anything and everything.
It might not be that similar but I remember after I watched superbad I watched Eurotrip.
The movie might've not aged as well as I remember though, I last say it when I was 15 and thought it was hilarious.
I have no shame admitting I liked this film, the only other alike that I have watched is Project X, definitely gonna save this post to check out others lol.