Animonsta Studios vs Nickelodeon

Connection:

Both are happy go lucky orange animated teenage boys who can control multiple elements at once

Both would meet a girl (Yaya and Katara respectively) who befriended them upon their arrival in a country (Rintis Island and Southern Water Tribe)

Both would form a team of heroes (BoBoBoiy's Gang and Team Avatar respectively) 

Both would have rivals who started out as villains (Fang to BoBoiBoy and Zuko to Aang) before reforming and joining their team

Both once had some/ their powers temporarily nullified by the villains which left them weakened (Retak'ka stole 4 of  BoBoiBoy's 7 Elemental Forms leaving him only to use Blaze, Ice and Quake, while Aang was struck by Azula's lightning in the Avatar State which severs his connection to the Spirit World and nearly ended the cycle). But in the final battle, they not only got it back but also gained new abilities (BoBoiBoy learned Elemental Fusion which allowed him to retake his Elemental Powers back and defeat Retak'ka, whereas Aang's back was pressed against a sharp rock which allowed him to enter the Avatar State once again and removed Ozai's firebending which Energybending)