Tort law often gives you some rather odd fact patterns; here's one I just came across, from Woods-Leber v. Hyatt Hotels of Puerto Rico, Inc. (1st Cir. 1997):

[Hyatt's] Cerromar Beach Hotel … in Dorado, Puerto Rico … occupies a picturesque oceanfront setting. Its verdant grounds are bordered on the west by a mangrove swamp which is under the protection of the Commonwealth's Department of Natural Resources. On the far side of the swamp lies Lakeside Villas, a residential subdivision which was being built at the time material hereto. Hyatt has no financial or other proprietary interest in the development of the subdivision. [P]laintiff-appellant Lynne Woods-Leber, a guest, was sunbathing near the hotel's pool. Suddenly (and without any apparent provocation) a wild mongoose scurried into the pool area and bit her. Because the mongoose carried rabies, Woods-Leber underwent a series of painful inoculations.

Woods-Leber sued, claiming the hotel was negligent, but the hotel responded with the No-One Expects The Rabid Mongoose defense—a winner:

[U]nder Puerto Rico law, a hotel-keeper owes its guests a heightened duty of care and protection…. Nevertheless, a hotel-keeper is not an insurer of its guests' well-being…. [A] hotelier is liable for a guest's fall on hotel premises only if the hotelier knew or should have known of a preexisting dangerous condition). Consequently, notwithstanding the heightened duty of care and protection, the hotel-keeper is not liable for harm unless the harm is reasonably foreseeable…. [T]he record permits only one conclusion: that Hyatt had no knowledge, actual or constructive, either of the mongooses' existence or of the incipient danger that they presented, at any time before the attack. The hotel personnel most directly involved in the matter (such as the head grounds keeper and the chief of security) submitted affidavits which made plain that a mongoose had never before been seen on the hotel premises; that no one at the hotel knew of the presence of mongooses in the mangrove swamp or otherwise in the vicinity; and that, prior to the assault on Woods-Leber, no wild animal of any kind had ever bitten any hotel guest. By the same token, there was no evidence from which a factfinder could conclude, without rank speculation, that the temporary food preparation and storage area presented any hazard or that Hyatt should have known the inauguration of a construction project near the mangrove swamp portended an influx of wild animals. Indeed, several previous construction projects had been undertaken near the swamp without incident. Finally, there was no evidence either that a non-rabid mongoose, unprovoked, was likely to bite a supine sunbather, or that rabies was prevalent in the area…. [If] an occupier of premises disregards a known general danger, or omits a precaution regularly taken by prudent persons similarly situated, a first attack might well be foreseeable (and, thus, actionable). But here, the plaintiff offered no evidence to support a finding of foreseeability …. Since a hotel-keeper, like any other owner or occupier of premises, cannot be held liable for that which it cannot reasonably foresee, the lower court did not err in granting Hyatt's motion for summary judgment.

Woods-Leber also sued under a Puerto Rico statute that imposes "strict liability on the possessor or user of an animal for any damages which the animal causes." The hotel's response: the Not Our Mongoose defense, also a winner: