Interactions from Characters from different franchises

[Sweet Snow]

It's not always how a fight breaks out, let's talk about interactions

Dr. Eggman and Dr. Doom could team up, but break up due to sheer ego, Sonic is asked to join the Avengers but refuses due wishing to be as free as the wind

As for a classic one, I don't think Goku and Superman would fight at all, at best some sparing or training, but never a death fight, Goku would look up to Supes due to his power and finally be matched, Clark tries to keep news of villains like Darkseid from reaching him, knowing he would recklessly go in for a challenge

 

[Cayde]

Lightning McQueen and Sonic could have a race to see who is faster.
Elsa and Rosalina would be good friends.