The final scene where Napoleon uses a dance routine to the song Canned Heat to win Pedro the school president election. This is further emphasized by the fact that the audience within the movie itself erupts into thunderous applause. Especially awesome, considering Don and Summer's reaction; when Napoleon finishes dancing, they just stare at the stage in smug amusement, confident that he just humiliated himself in front of the entire school. Moments later, everyone in the auditorium starts cheering—and their smug expressions vanish as they look around and realize that everyone else loved it.
Napoleon's fight with Uncle Rico. After Rico told Deb that Napoleon said she'd look better with breast implants and has been a general prick the entire movie, Napoleon throws a grapefruit at his van (and at Rico himself!), before actually getting out of Rico's grip and fleeing. Also counts as a Funny Moment and Mundane Made Awesome.
Rex showing up to defend his wife. It's implied that he gives Uncle Rico the ass-kicking he's been earning the whole movie.
Rex: C'mere, boy!
Napoleon's Dynamic Entry in The Stinger showing up to Kip and Lafawnduh's wedding riding a "wild honeymoon stallion" he claims he tamed. Whether or not he actually tamed it, just the fact that he was able to get a horse to give to the couple as a wedding present is impressive.