Guardian's Crusade is an obscure but very well-regarded entry in what I'd call the "buddy RPG" genre, where the player has a partner character that grows and changes throughout the game (see also Okage: Shadow King on the PS2). The little blob creature next to the knight there is a virtual pet that you can feed items to and play with during the storyline. Depending on your choices, he'll do a variety of actions during battle – performing powerful attacks, healing you, or transforming into a friendly monster, etc. – and can gain new abilities for use in the overworld. You don't have any other party members, and he can turn on you if you mistreat him, so finding the right ways to raise him well throughout the standard JRPG jaunt is essential (and a huge part of the the fun).
The game also has an excellent presentation – the characters are extremely simple and cartoony (think Little Big Adventure), but have a ton of unique animations and personality in and out of battles. Like many PS1 RPGs, this game's storyline is a heavy parody of traditional role-playing adventures from the NES/SNES era, so there are plenty of laughs and cute moments to keep you moving forward. The tag-along monster is very endearing – it's essentially a boy and his pet story – as is the relationship between the player character and the little mom-fairy who's the third member of the team. I'm not really one for long-form JRPGs, but Guardian's Crusade is a welcome exception to that rule. (The soundtrack is also
extremely rad.)