Thread:KingOfSpriters13/@comment-5891090-20130201184123/@comment-4111066-20130201191934

Turrets from Portal appeared in Shoot Many Robots, a game which also contained Weapons from Team Fortress 2

Team Fortress 2 characters appeared in Sonic and All-Stars Racing Transformed

Sonic and Mario appeared alongside each other in Super Smash Bros Brawl

Mario is in Mario Kart Arcade GP 2, a game which contained Pac-Man