Castle Crashers is an incredibly charming beat 'em up/hack-and-slash by independent studio The Behemoth (of Alien Hominid fame back then) which main specialty is its seamless real-time four player co-op and the vast array of characters you can unlock and play as, nearly every common enemy in the game is unlockable and playable with their own set of magic too, it's some pretty neat stuff! Every so often there's a gimmick in the stage that keeps it sorta refreshing to keep going and the whole thing is not that long if you know what you're doing.

Of course, this game was made in the rising age of Newgrounds so the artstyle and comedic tone that is reliant on slapstick humor is pretty distinguishable and unique to the studio, thing that heavily benefits the character/enemy design coupled with the absolute variety of stages to go through with your team.
Then there's the actual gameplay side of things which I can't really say for certain I have a huge grasp on since this is probably the first ever beat 'em up I've actually finished in my life, but it's some pretty basic stuff with combos and magic you can do then experience points you can gain to actually spend on bettering your stats as a whole, bit of a Terraria situation where the progress on your characters is actually you keep across many games, so if need be you can demolish everything with a high level character for late game completion goals.

In general it's just a great (and by now, nostalgic even) time to have with friends, game incentivizes cooperation but at the same time a lot of competition, at least when you're forced to battle each other, collect treasure or beat the most enemies to have a better build and destroy everything in your way. I do wish there was more of an excuse to revisit it besides the Insane Mode difficulty bump, which I'll most likely play at some point in time but after not having finishing the game in so long, I think I'm alright for now.

Shoutout to Pancake, Martix and Jakob for playing with me in my birthday. 🫡