In the Rise of Sqeegee 7

Luigi is Mario's brother who's first appearance in the Rise of Sqeegee series is in the Rise of Sqeegee 5. He has appeared in the next two episodes as well, fighting Sqeegee alongside Mario. He first fought Sqeegee when Mario was about to be finished off by him, until Luigi showed up and kept repeatedly kicking Sqeegee in the groin. Sqeegee hurt so badly that he teleported away. Later he returned during the fight in space and fused with Mario to defeat Final Sqeegee. When he fought Sqeegee after he came back to life, he and Mario ended up losing. He came back once again in the Rise of Sqeegee 7, fusing with Mario to form the invincible warrior, Russmarrs2.