The live-action Scooby-Doo underwent multiple changes, with its original ending being altered to transform Scrappy-Doo into a villain. Despite its poor critical reception, Scooby-Doo has gained a cult following among those who grew up with the adaptation. However, the movie suffered several cuts and story changes, with one of the biggest additions being a new ending with Scrappy replacing two other villain plans.
Scooby-Doo ends with the gang disrupting the Daemon Ritus ritual, only to discover Scrappy is the evil mastermind behind the Spooky Island mystery. Debuting in 1979 as Scooby’s courageous nephew, Scrappy is notoriously viewed as a franchise blunder. The reveal that he is the live-action Scooby-Doo’s villain is a memorable twist, although it seems more like an in-joke than a logical decision.
The R-rated cut of Scooby-Doo had the demons originate from outer space, and this would have played into the movie’s original ending. Speaking on the DVD audio commentary, the director and producers recalled their desire to choose a villain connected to the gang over an “anonymous monster.” Except that test audiences weren’t thrilled with Scrappy’s evil depiction, resulting in two endings being shot, one of which would have brought back the Luna Ghost/Old Man Smithers (Nicholas Hope).
According to director Raja Gosnell, an early draft of Scooby-Doo featured an entirely different villain, albeit one who made far more sense combined with the Daemon Ritus plot. Although he didn’t elaborate on the Scooby-Doo movie's original villain plan, Gosnell did reveal, “This monster flew down from the sky and he was going to use the ultimate power to rule the world.” This could have better explained why the Spooky Island guests’ souls were being collected, instead of Scrappy simply absorbing them to transform from a tiny pup into a giant. Gosnell thought the original monster was “really unsatisfying,” as it wasn’t known to the gang and “didn’t really come from anywhere”. This resulted in Scrappy becoming Scooby-Doo’s villain, intended to play on viewers’ dislike for the character. Accordingly, the filmmakers made Scrappy even more irritating than usual, with a flashback involving him attempting to take control of Mystery Inc. and urinating on Daphne (Sarah Michelle Gellar). Despite this change in characterization, test audiences still weren’t too pleased with Scrappy’s villainous turn.
Speaking on the DVD commentary, producer Richard Suckle admitted that “a lot of people we previewed the movie for had some concerns with Scrappy.” Although parents were aware Scrappy wasn’t well-liked, they didn’t understand why Scooby’s nephew was suddenly evil. An explanation for his behavior was hastily added, with producer Charles Roven revealing he was changed to be “misguided and actually taken advantage of by the creatures.” However, the filmmakers’ solution was to merely have Velma (Linda Cardellini) state Scrappy was corrupted by the Daemon Ritus’ mysterious power. This idea could have been taken much further, showing how Scrappy was manipulated by the demons and reduced to a naïve pawn. This would have made him a sympathetic villain, as opposed to a merciless monster loathed by the Mystery Inc. gang. Scooby-Doo’s filmmakers knew Scrappy’s actions could prove controversial, so another ending was shot with a different villain as a backup plan.
Old Man Smithers was intended to appear as an onlooker in the crowd on Spooky Island – just one of several deleted scenes from Scooby-Doo’s R-rated cut. However, an alternate ending would have seen Smithers unmasked as the movie’s villain. It’s unclear how he would have factored into the main plot, making little sense since he was caught in Scooby-Doo’s opening. The confusion over Smithers’ role emphasizes the filmmakers' difficulty in completing the movie. Reshoots and multiple cuts demonstrate there was no clear plan for the ending. Rowan Atkinson’s Mondavarious almost didn’t return, and Gosnell revealed Shaggy’s (Scream's Matthew Lillard) kiss with Mary Jane (Isla Fisher) was cut so as not to “isolate Scooby from the win.”