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.
Anti-Climax Boss: The Final Boss battle against Croog. The game-play is centered around using your drill in innovative ways. So how does this one particular battle play out? The Drill Dozer breaks down and Jill takes out Croog with a single punch.
Doubles as Hilarious in Hindsight for fans of Tengen Toppa Gurren Lagann when you realize it's very similar to how Simon had to punch out the Spiral King when his gunman broke down. Remember, the game released in Japan in 2005, approximately 2 years before Gurren Lagann's start, let alone when that scene aired.
Freud Was Right: A pink-haired school girl drills into holes that always fit just right.
That One Boss: The Drizzler, boss of Metal City Skyline, is a pain in the ass to fight. There is a very high chance of you dying repeatedly during the obstacle courses it puts you through in the first half of the fight (especially the third one; it's a straight up vertical course, but electric ladybugs and the rather poor control over the drill propeller can create serious frustration). Although things get significantly easier as soon as you hit the second half (from the second phase, all you have to worry about is the pieces of itself and the occasional laser, on which you have to hit it after said laser fires), you'd better hope you have some health left over, lest you'd likely suffer having to do that all over again.
The boss of the first Metal City is a possibly even worse, as the boss launches blue bombs that need to be drilled into with R button, and red ones with L. The boss is also very tricky about launching these and forces you to think quickly about which button you need to press. That and you need to time shooting the bombs back.
That One Level: Area 4-2, Metal City Skyline. Pilotting the Air Dozer is nowhere close to easy.
CLINK PRISON. The ONE-BLOCK-HIGH JUMPING in the first half, the poison turrets, the infrared sensors, the annoying cannon clamps, and the stupid jetpack guy with the poison-dart machine gun. Oh, and the Towerbot. The secret level is even worse.