The short opens on a strange mountain trail on Halloween Night. Shadows of Frankenstein's monster, a witch, and a devil are seen moving toward the Mighty Eagle's cave.
Mighty peers out of his cave to see the three shady figures, who are just the Blues in costumes, who are trick-or-treating. After Mighty gives them a candy, the Blues continue on their way around the island, until they see a large, orange, blobby creature lurking in the woods. Each of the Blues imagine what kind of monster it could have been, but then laugh it off and assume that it is part of Halloween, and pursue the unknown creature.
The Blues look around the forest for the creature, and see that their candy bucket is shaking. They look inside the bucket to find Bubbles, who is happily eating their candy. Suddenly, the Bad Piggies appear, wearing King Pig masks and bringing candy to their fortress. The Blues hide themselves and the bucket behind a tree, but after the pigs are gone, they realize that Bubbles somehow ended up in one of the Bad Piggies' candy buckets.
Then they find that one of the Bad Piggies dropped their mask, so they put it on and follow the Bad Piggies to the fortress to get Bubbles. The Blues, with their Pig Mask and their own candy bucket, actually fool the Corporal Pigs, who are guarding entry to the fortress.
When the Blues get inside, they see all the Bad Piggies dumping candy onto a conveyor belt. The Blues then spot Bubbles, who has been dumped onto the conveyor belt with the candy, as the pigs are unaware of it. The King Pig, who is dressed as a vampire, is sitting at the end of the conveyor belt, and opens his mouth so that all the candy falls into it. Another pig, dressed as a mummy, turns the lever to "slow".
The Blues quickly get to the lever that controls the conveyor belt, and make it stop. The King Pig gets angry and calls on the Corporal Pigs, who hop onto the conveyor belt and see Bubbles. The Blues pull the lever to "slow reverse", making the conveyor belt go the other way and toppling the Corporal Pigs off it. But then the Corporal Pigs hop onto the other side of the conveyor belt. The Blues switch the lever back to "slow". Bubbles, who has no idea of his troubles all along, has still been happily munching on candy as the Blues keep switching the lever around. Suddenly, they accidentally turn the lever to "fast reverse", and the King Pig gets pulled onto it by mistake, knocking all the Corporal Pigs and almost all of the candy off.
Bubbles, seeing his favorite kind of candy, and the King Pig, seeing it too, both try to get it until the conveyor belt explodes. Bubbles, the King Pig and the piece of candy are then shot up into the air. Bubbles and the King Pig both lunge for it in slow motion, but the King Pig ends up catching it in his mouth.
For the first time, Bubbles actually gets very angry, and uses his power of inflating to enormous size to squish the King Pig against a wall, making the piece of candy shoot out of his mouth and into Bubbles's beak, making him happy again and zoom around the room while deflating, damaging the fortress even more, before landing back in the Blues' candy bucket, which was emptied.
The Blues then befriend Bubbles and leave the fortress, which collapses as they leave.
Of all the shorts to feature the same art style, this is the only one that displays the title at the beginning. The other shorts usually don't show the title until the end (except for the Wreck The Halls Short Movie).
Possibly, the Blues dumped their candy onto the conveyor belt.
When the Blues are watching Bubbles (in the fortress), he looks like the orange creature in the woods seen earlier.
King Pig's appearence is very different than his later toons version, mostly due to it even thought yet.
The Ham'o'ween Short was made for the debut of Orange Bird.