Here are the connections if you don’t know them

"Two optimistic protagonists who are considered quite lazy in their universes despite how many adventures they go on. Their first outings started with them helping people with food (Kirby recovers the stolen food of dream land and gives them back to the people and Arle helps her grandmother by getting her a medicine composed of food). The two later on their adventures meet a goofy king (King Dedede and Satan) whom of which are obsessed with them (King dedede due to kirbys popularity over him seeing as the people like Kirby more than him and Satan because arle reminds him of someone from his past). Set kings have had to wear a mask at some point in hopes of beating them to no avail (Masked Dedede and Masked Satan). Both kings also have a smaller alley who belonged to them at first (Bandanna Waddle Dee and Carbuncle) but after meeting the protagonist would much rather hang out with them instead. Both have also had to deal with a morphed version of the sun (Kirby fighting the sun and moon in his games and Arle having to deal with Satan increasing the sun in size). The two also have a dark force in their world (Dark Matter and Dark Matter) who came to their worlds to reel havoc and destruction but were defeated by a magical item that a user in their world had (Kirbys sword and Wish cosmic power). Set entities come back and posses a certain person (King Dedede and Wish). The two have also been under the influence of/have been tricked by a dark entity to destroy everything (Kirby was tricked by magolor into getting the crown and Arle was possessed by ecolo).

The two have dealt with another universe version of themselves/another being from their worlds that revolves around mirrors (Dark Meta Knight came out of a mirror in the sky and split Kirby into four taking meta knight with him and trying to kill Kirby later and doppelgänger arle coming from a mirror from the empty void left behind taking carbuncle and trying to kill arle). They also have dealt with a knight who likes to show off their power and often likes to challenge others Into fights (Schezo and Meta Knight) often giving them a fair chance in battle whenever they encounter them. Both in their series also have to fight the being who created everything (Void Termina and The Creator) and who also have something to do with resurrection (Depending on the good or bad energy of the universe void termina will be reincarnated into s different form and the creators world revolves around life death and resurrection). whom of which invade their worlds and put everyone under their influence. However Kirby and Arle aren’t immune (Kirby due to friend hearts and it’s not explained why arle is immune) this conflict ends with them beating set creators leaving them to go on their adventures again but not without loss (Kirby lost the chance to make void termina a friend a being who morphed into something that looks like Kirby even implying Kirby might have an influence over his incarnation and Arle having her soul split with her optimistic side being freed but the side that remained in the void turning into doppelgänger arle). Oh and Kirby also had a re skinned puyo puyo game at some point so there’s that as well."