To access a hidden level in Tealand, go to Level 5-2 and go up the clock tower. Continue upwards after reaching the next area. There will be an area that forces you to move right, accompanied by an arrow sign telling you to go up. Pass the sign, and fall into a small gap. Walk to the right and through the false wall. Continue climbing all the way to the top. There will be a large white chest, just like at the end of every stage. It will unlock Level 5-?, which is located in the clouds. Henry will begin the level in a small blimp.
The following hidden suit pieces have the corresponding effects:
SUIT PIECE - EFFECT The Gentleman's Bowtie - Weapons use less Super Meter. It is found in Level 5-1S. The Gentleman's Monocle - Puzzle Meter refills faster. It is found in Level 2-3S. The Gentleman's Mustache - Enemies drop tea cups when defeated by your Robot Suit. It is found in Level 3-5S. The Gentleman's Vest - Reduced damage from lava and spikes It is found in Level 4-1S. The Gentleman's Wallet - Gems are worth 15% more. It is found in Level 1-4S.
This strategy can be used with any enemy, though it works particularly well for the majority of bosses. Once you obtain the boomerang, do not trade it for another sub-weapon. The boomerang, when charged to its fullest level with puzzle combinations, will home in on the opponent and cause most to stop attacking.