Great game.SHould get it for your PS2
If you were expecting an adventure game, one in which you're probing various characters for info, digging up clues, and generally unraveling mysteries, you might be surprised to learn that First Frights is actually a beat'em-up. There is a bit of platforming and item hunting tossed into the mix, but for the most part, you'll be doing a lot of brawling.
Throughout each of the four gloomy, boring worlds, players will beat up dozens upon dozens of bad guys. Mutant sea creatures, witches, evil creepy dolls, etc. None of this gets an explanation. The game does throw in the mystery element by having the player find clues, but usually the cutscene makes it extremely obvious who did it. But when it's time to wrap up the mystery they don't explain how the middle school gym coach commanded an army of ghosts and monsters. I'm sorry but after decades of the team being able to easily explain how the bad guy did everything (except for that one time with those zombies), I expect Velma to be able to explain where murderous flying witches came from.
Much like the LEGO games there is a free play where players can go through levels with other characters to find secrets. All of the secrets end up being more Scooby Snacks, which are used to buy costumes that you can then use when you replay the level on free play (which you just did already). It's not very useful or exciting, especially since you already earned plenty of Scooby Snacks during the initial run through. The trophies are a nice attempt at offering something extra, but there's no point. Making the trophies unlock secret costumes would have added more.
Overall it is a good game so you should get it now.