*Due to the amount of in-company crossovers, I consider the two companies a game on their own.
Nick’s Super Brawl 3 features the Teenage Mutant Ninja Turtles.
The Rabbids appear as playable characters in TMNT Smash-Up, who also appear in Academy of Champions.
Altair from Assassin’s Creed also appear in Academy of Champions, and Ezio appears in Soul Calibur V.
Link is featured in Soul Calibur II and Super Smash Bros with Sonic.
Ralph from Wreck-It Ralph appears in Sonic and All-Stars: Racing Transformed and Disney Infinity, which is Disney itself (combined with Kingdom Hearts).