Plastrification (also known as being Plastered) is a devastating, debilitating affliction of the plastic beings of the Plastic World
If one Plastic being from the Plastic World spends too much time in any other world, they gradually turn into an inanimate toy. The movement becomes severely limited, up to total freezing. Plastic beings can only emit grunts after the last phase of Plastrification. But this already old affliction becomes extinct after the invention of the vaccines, allowing to Plastic beings remain much longer, if not forever. The only way to reverse the effects of the vaccine is using Plastrification serum.
Plastrification usually spells doom for any Army Men plastic soldier or any Plastic being from the Plastic World unlucky enough to become afflicted by it. The concept is first explained by Scorch in his namesake mission during Sarge’s Heroes events, and later in public by Professor Foreyes in a video. Before Sarge’s Heroes 2 events, General Plastro was left stranded in the Real World, without a way back home, and as such, he was Plastered. But this didn’t happen with plastic soldiers molded in the Real World, that at the same time have no problems staying in the Plastic World. But in any other world the affection caught them with the same symptoms.
At some point later, Dr. Madd created a serum that reversed Plastrification, and gave it to Brigitte Bleu to free General Plastro from his ailment. The serum was blue in color, and emitted from Brigette’s perfume bottle (in the N64 version of events it was funneled through a flamethrower-like device) It could also bring life to inanimate objects in the Real World as well, as Plastro and Brigitte traveled to a toy store and took control of robot soldiers there by giving them the serum.
Dr. Madd began to mass produce the serum out of a refrigerator in the Real World, transporting it via Train to his Castle, where it was stockpiled and distributed. This production was later sabotaged by Sgt. Hawk and Bravo Company, who blew up a bridge to stop the transit trains, raided the fridge, and then launched a strike against Dr. Madd’s castle, destroying most of the serum.
At some point, a serum that causes plastrification was also developed, presumably by Dr. Madd. It was pink in color, and was used by Brigitte to plastrify Sgt. Hawk. Very shortly afterwards, Vikki Grimm unplastered him using the first serum.
After the events of Army Men: Sarge’s Heroes 2, Plastrification seems to be relegated to a minor concern. Brigitte Bleu seems to be living in the Toy Store full-time during the events of Portal Runner, and the Green and Tan build elaborate military bases in the Real World in Army Men: RTS and Army Men: Air Combat. Though from there Plastrification is not mentioned by name, the existence of non-army-men toys in the Plastic World who are animated, such as the villagers in RTS or the Teddy Bear in Air Combat events, imply that the effects of the De-Plastrification serum continue to affect the setting of the Plastic beings.
Plastrification, while seemingly a prevalent theme in Army Men: Sarge’s Heroes 2 events, was completely ignored in several other historic events, even in the past. Anyway in the past the Army Men didn’t spend much time in the other world. The stays in the Real World prior to Sarge’s Heroes were short and sporadic visits, limited only to secret missions for each of the nations.
While it does not seem to exist outside of the Sarge’s Heroes chain of events, even other historic events that take place some time later, like Army Men: RTS, ignore the concept. Units are seen moving, fighting, and even being created in the Real World for extended periods of time with no hindrance whatsoever. More than sure the most likely reason is that these soldiers were created in the Real World and did not really come from the Plastic World, having to do in some way with the different rules of the reality of each universe.
An in universe argument could be made that by the time the events of the game took place, the vaccination serum mentioned by Brigitte Bleu became widely available to all active armies in the Real World, thus eliminating the effects of Plastrification altogether.
In any case, these changes happened quite quickly and there was no correct record about it, or these records were simply deliberately deleted. If those of us who are in this world so long after those events do not know or hear about vaccines, perhaps this magical elixir was applied in some way to the molding processes of plastic beings, and the rest was vaccinated.
Other particular cases
One of the coolest weapons of Plastro’s Tan Army, is the dreaded “V-Bot,” which is a toy robot that comes to life once it is brought back from “Human World” into Plastic World. Any inanimate plastic object that is brought back (using the Portal) from Real World into Plastic World becomes animate.