Trixie and Veronica are not seen morphing into their costumes.
This is so far the only Halloween special for the series.
Transformers - The Jack-O-Bots name is a play on the "Autobots", although the Jack-O-Bots themselves are evil while the Autobots are good. (This makes them more similar to the Autobots' enemies, The Decepticons)
Toys Я Us - Vicky's insult, "Where did you get the stupid European costumes, Dorks R Us?" contains a play on the chain's name.
When Veronica, Trixie, and the other rich kids appear on Timmy's doorstep, Veronica's pupils are mistakenly colored pink. After Trixie tells her to polish her costume, Veronica's pupils return to their normal blue.
When Cosmo and Wanda appear as cats during the scene where Timmy meets with Mark Chang, Wanda is colored green and Cosmo is pink.
Although the Jack-O-Bot costumes are wished back into normal, inanimate objects, they later appear on Unwish Island as sentient beings.
When the Pumpkinator prepares for detonation after morphing into its' doomsday device shape, it begins audibly counting down the final minute ("59, 58, 57...") But when Timmy starts speaking, it remains silent for the rest of the countdown.