- Awesome Music: Brennan's rendition of Por Ti Volare.
- Better on DVD: The unrated version adds in better jokes.
- Crosses the Line Twice: Many scenes, given the fact that it's a R-rated comedy:
- "Brennan Has A Mangina" and the fact that Nancy actually joined in on it.
- Brennan and Dale dressing up respectively as a Nazi officer and a Klansman to scare away prospective homebuyers.
- Also, during the credits when the two main characters beat up a bunch of children at a playground (although, in the context of the film, you're actually rooting for Brennan and Dale).
- Cult Classic: The film's gleefully juvenile humor and highly quotable dialogue have earned it an enthusiastic following long past its middling theatrical reception.
- Ensemble Dark Horse: Brennan and Dale's parents steal the show in many cases, due to Doback's increasing temper and hearing Mary Steenburgen say the most hilarious things in that soft, pleasant voice.
- Hilarious in Hindsight:
- Memetic Mutation:
- "Boats n' hoes!"
- "Brennan/Dale has a mangina!"
- "So many activities!"
- "Did we just become best friends?" "YUP!"
- Orphaned Reference: During the argument in the house after the boys wreck the boat, seen here, Brennan references "fake hearing devices", as he threatens to stick one in Robert's backside. This seems out of place and without explanation in the theatrical cut of the film, but this deleted scene turns this throwaway line into a minor Brick Joke.
- Playing Against Type: Compared to Adam McKay's previous works with Will Ferrell, in spite of it's silly premise, Step Brothers is more of a grounded comedy-drama with a greater emphasis on how Reality Ensues with the Manchild trope. At one point, Mc Kay even considered making the film an actual drama.
- Some Anvils Need to Be Dropped: Downplayed, but Brennan asking his therapist "How do I be an adult" shows that some people simply have a harder time transitioning into adulthood than others.
- Unpopular Popular Character: The two main characters. In-Universe, most people cannot stand them due to being such immature losers, but viewers of the movie find them utterly hilarious.
- The Woobie: Alice.
- Jerkass Woobie: Dale, Brennan, and Dr. Doback.
YMMV / Step Brothers