James the Cricket
James the Cricket is a cricket within the confines of the dungeon in which your players currently exist. The party will come upon him when he hops on one of their shoulders. James knows the dungeon like the back of his...uh...leg and will talk to the party about secret rooms, hidden traps, other residents, etc. Essentially, he is a hopping, talking dungeon guide like the DM would use, but for the players.
Here's the problem: James the Cricket is a cricket. He communicates the way all crickets do - incredibly loud chirping. For James, this means incessant chirping in a party member's ear as he talks with them. If no one in the party speaks Cricket, all they hear is really loud, annoying chirping. Of course, this is essentially a beacon for Other Things in the dungeon to locate the party.
James the Cricket can be killed like any cricket. Here's the problem: he is immortal and very forgiving. If the party kills James, he will spawn in the next room they enter and hop on another party member's shoulder to resume his conversation with them. The only difference is that he is now twice as loud, as he assumes the party simply didn't hear him the first time.
This horrendous idea brought to you by that stupid cricket outside who won't shut up.