The Meatlings are the secondary antagonists of the Phineas and Ferb episode "Excaliferb". They are monstrous creatures who were created by the evil wizard Malifishmertz of the Malifishmertz Evil Tradesman Association to serve him.
The Meatlings were created by Malifishmertz to conquer the Tri-Kingdom Area. He explains that they are created by using the most hideous substance known to man: canned meats.
Though Malifishmertz was successful in creating the Meatlings with the help from his assistant Lawn Gnorme, they weren't as intimidating as one would expect. However, Malifishmertz explained that the Meatlings would become bigger, stronger, and more evil looking by exposing them to water, which would explain why he cast a rain spell so that they would grow bigger and stronger.
While the heroes' were journeying toward the enhanced sword Excaliferb, Malifishmertz sent a small army of his Meatlings towards them in hopes of getting rid of or at the very least incapacitate the heroes. Fortunately, the heroes managed to evade the Meatlings and continued on with their journey, using the magic sword to summon an army of monsters to their side.
Later on, during the battle between Malifishmertz and the heroes, several Meatlings (who had increased far bigger in size) joined by Malifishmertz's side, taking down several of the summoned monsters. Eventually, Sir Ferbalot cast a spell on himself to transform himself into a scary Medusa-like monster, turning the Meatlings into stone, contributing to Malifishmertz's capture (though he later escapes during the heroes' bonfire party).