VGFacts

someone dressed as Bang from Clash at Demonhead can be seen in the crowd in the halloween party level







may or may not be considered trivia: The movie's band's poster for Clash at Demonhead resembles the one used in the game three days after its release.  

(Scott Pilgrim vs. The World: The Game)



(Scott Pilgrim vs. The World movie)

Tom, one of the game's enemies, is based on Tom Guycot from Clash at Demonhead, who serves as one of the villains within that game. 

Picture of Tom: 
https://scottpilgrim.fandom.com/wiki/File:Tom.jpg







AND the band is based on the game of the same name



Sources: 
https://gamerant.com/scott-pilgrim-vs-wo...ster-eggs/

https://www.reddit.com/r/ScottPilgrim/co...tle_cameo/