That's an interesting question! The goal, so to speak, of the fungus, is to infect as many people as possible, and to remain stealth, so it's not going to cause any drastic changes to behavior like setting rooms on fire, but something like lying in wait, which sounds more like a behavior, could definitely be a side-effect. Think minor, strange behavior glitches in service of infection rather than making you into, to what other people, would look like a completely different person.