This is in memory of Harold Ramis, who between Ghostbusters, Stripes, Caddyshack, Animal House, and Groundhog Day gave me more movie quotes than anyone aside from Dave Thomas & Rick Moranis and the entire Monty Python crew. So you know, he's got that going for him.
These are prefixes you can add to existing GURPS creatures of all kinds. Collect all three!
Spores - For plants and slimes only, generally, but it's DF, so go nuts. The creature shoots a cloud of hallucinatory spores!
Statistics: Add Spore Could (Resisted by HT-1): Range 10, Respiratory Agent, Area Effect (3 yard diameter); Persists for 10 seconds. Failure to resist causes hallucinating (see p. B429) for 1 minute per point of failure. Costs 1 FP per use.
Mold - The creature is covered with a sickly, disease-carrying mold. It's easy to see (+5 to Per rolls to spot) but it might take an IQ-based Survival or Naturalist roll to identify the danger!
Statistics: When struck, the creature gives off a cloud of poisonous mold particles. Poisonous mold (Resisted by HT): Failing the HT roll causes 1d toxic damage, success reduces the damage to 1 HP. Failure by 5+ also causes choking (see p. B428). Creatures with Doesn't Breathe are immune to the choking effect, but suffer the toxic damage normally.
Fungus - A fungoid version of the base creature. Fungoid creatures often have lower IQ than the animal version of the creature, but this isn't required.
Statistics: Change class to Plant. Add Doesn't Breathe; Doesn't Sleep; High Pain Threshold; Immunity to Metabolic Hazards; Injury Tolerance (Homogenous, No Blood).