Real-time clock / time of day

While the game doesn't look any different in the day or at night, there are distinct areas of the game you need to pay attention to the time of day for. Illusion Village is an area only accessible from 3pm to 6pm, and the School Basement level has exclusive Robopon to catch at night.

"GB Kiss" & Other Peripherals

The infamous GB Kiss technology in the Robopon Sun, Moon and Star versions was a setup of bespoke hardware built into the game cartridge which allowed infrared communication. In Robopon, you use your TV's remote control to influence different aspects of the game! Wowie zowie! IR is also used for collecting event-specific Robopon or items.

"Remote Shower"

At any time, you can also just give your Robopon what the game instructions call a Remote Shower, which might boost some of their stats. This is, like many aspects of Robopon, a charmingly bizarre idea. The game cartridge also had a built in speaker which you could set to alert you to various events in the game even when your Game Boy is turned off.

GB Kiss - further reading

You can find a LOT of information about GB Kiss on Esteban / Nectaris' website! Apparently this was not just Robopon-exclusive tech but was included in a few other games, and there was even a GB Kiss modem made, however it didn't see much commercial adoption at all. I highly recommend Esteban's website for more detailed info.

Events Calendar

By inspecting various big stuffed teddy bears throughout Porombo Island, you will find the delightful, species-ambiguous and aptly-named Schedule Man! He presents you with three treasure chests containing powerups of various kinds. These upgrades/downgrades don't just influence your Robopon's stats - they also influence things like how many rare Robopon you run into in the wild and even how fast you walk. When you get a powerup from the Schedule Man, you are asked to place the powerup on a time of day and at those times it will be active!

Algorithmic Movesets

Your Robopon are machines, and so they need different hardware (Parts) and Software, as well as occasional CPU upgrades. Unlike in Pokemon, the moves that your Robopon can use in battle are not innate to them, but a result of Parts and Software working together. For instance, if you equip the THROWER part, and the FIRE software, your Robopon can use the move FIREARROW. If you have both the FIRE and WATER software, your Robopon can use the move STEAM.

This makes battle a lot more interesting and complex, because you don't necessarily know what moves your opponent will have based on what Robopon they send out to battle. It also means that if you get a specific Robopon, you aren't "locked in" to a specific, immuteable moveset that Robopon has - you can get creative and mix and match Parts and Software.

[silly] Minigames!

Instead of "normal" battles, you will sometimes be challenged by characters to a minigame. There are 4 types of Minigame:

Speeder
in which your Robopon "speed" through a little maze, the first one to get to the bottom cube thing wins!

Puncher
is a strongman test of might. Your Robopon with the highest Attack stat will do the best at it, although you also have to time it so that the random numbers on the Puncher machine give you even better odds.

Sheilder
is a pretty interesting concept. You are presented with 6 cards that are face down. You and your opponent choose a card, and that card determines what attack you have to defend against. If your Robopon is the last one standing - hence needing high Defense stat - you win!

Jumper
is an Olympic-style long-jump competition.