The two unprepossessing gentlemen who installed or planted the devices, depending upon your sympathies, have been arrested and charged with planting hoax bombs. You may be wondering whether they can be convicted.
The statute in question, Massachusetts General Laws c. 266, Section 102A½ says:
(a) Whoever possesses, transports, uses or places or causes another to knowingly or unknowingly possess, transport, use or place any hoax device or hoax substance with the intent to cause anxiety, unrest, fear or personal discomfort to any person or group of persons shall be punished by imprisonment in a house of correction for not more than two and one-half years or by imprisonment in the state prison for not more than five years or by a fine of not more than $5,000, or by both such fine and imprisonment.It seems clear that these two numbskulls put the devices in place. It doesn't seem like all that much of a stretch for a jury to find that these were put in place "with the intent to cause anxiety, unrest, fear or personal discomfort." The whole point of crudely animated cartoon characters flipping off passers-by would be to épater la bourgeoisie.
(b) For the purposes of this section, the term "hoax device" shall mean any device that would cause a person reasonably to believe that such device is an infernal machine. For the purposes of this section, the term "infernal machine" shall mean any device for endangering life or doing unusual damage to property, or both, by fire or explosion, whether or not contrived to ignite or explode automatically. For the purposes of this section, the words "hoax substance" shall mean any substance that would cause a person reasonably to believe that such substance is a harmful chemical or biological agent, a poison, a harmful radioactive substance or any other substance for causing serious bodily injury, endangering life or doing unusual damage to property, or both.
(c) This section shall not apply to any law enforcement or public safety officer acting in the lawful discharge of official duties.
(d) The court shall, after a conviction, conduct a hearing to ascertain the extent of costs incurred, damages and financial loss suffered by local, county or state public safety agencies and the amount of property damage caused as a result of the violation of this section. A person found guilty of violating this section shall, in all cases, upon conviction, in addition to any other punishment, be ordered to make restitution to the local, county or state government for any costs incurred, damages and financial loss sustained as a result of the commission of the offense. Restitution shall be imposed in addition to incarceration or fine; however, the court shall consider the defendant’s present and future ability to pay in its determinations regarding a fine. In determining the amount, time and method of payment of restitution, the court shall consider the financial resources of the defendant and the burden restitution will impose on the defendant.
So, the question would seem to be whether a person could reasonably believe that these were devices "for endangering life or doing unusual damage to property, or both, by fire or explosion." Notice that the intent of the accused is not relevant here. If they intended to cause personal discomfort, they don't have to have concluded that the devices could reasonably be mistaken for bombs. I do wonder whether the reasonable person here is a reasonable post-9/11 person who follows the news from Iraq, where IEDs are all too common? In any event, while a conviction isn't a lock for the prosecutors, there is real exposure here.