Halloween
Halloween is an Earth holiday in which humans dress up in strange outfits that make them look like other people or things. It is usually celebrated on October 31, and is a ritual to celebrate the end of Summer which started in Ireland many centuries ago, although it has evolved significantly since then.
Fiction
Legends anthology
Carlos, Rad and Alexis attempted to explain Halloween to their Mini-Con friends, and ended up resorting to taking the trio Trick-or-Treating with them. The Mini-Cons were confused by the human custom, and the way that Rad explained that they could "t.p." houses which didn't give out candy, but soon got into the spirit of the holiday. As a mark of their veneration of their human friends, the Mini-Cons took the tradition back to Cybertron with them, and thousands of years later, the Mini-Cons still went out Trick-or-Treating on Halloween. Something Robotic This Way Comes
Animated cartoon

On Halloween night, Bumblebee and Bulkhead went Trick-or-Treating with Sari Sumdac. They were in for a trick when Blackarachnia attacked, turning every dumb stubbie and... Um... leafie into older, wrinkly versions of themselves. Ew. Along Came a Spider
Notes

- The comic issue "Ghosts" was advertised as a "Halloween Special Edition".
- There have been Transformers costumes over the years. Noteable examples include:
- The 1986 Collegeville Costumes line featured several Transformers Halloween costumes and masks for children. The masks were made of flat styrofoam and included a hinge to flip the mask up and down. The costumes consisted of a vinyl one-piece smock and a simple plastic mask with an elastic band.
- For 2010, Several companies came out with different types of Transformers-based costumes for children and adults (including sassy adult women versions of Optimus Prime and Bumblebee).


