On this day in 2016, the Ready Jet Go! episode "Jet's First Halloween" premiered. The characters' choices of costumes were very interesting
Mitchell dressed up as Sherlock Holmes, "the greatest detective of all." Mitchell is a kid detective (or at least he tries to be), so it makes sense that he looks up to Sherlock Holmes and dresses as him for Halloween.
And Cody is Watson. This represents how Mitchell wants Cody to act more like his detective assistant, however, Cody would rather laze about than help Mitchell with his detective work.
Sydney being Commander Cressida for Halloween is pretty much a given, since she is a big fan of Commander Cressida comics.
Mindy dresses as her teddy bear, Stuffy Bear, who has been seen in a few episodes such as "Solar Power Rover," "Jet's Time Machine," "Mindy Turns Five," "Sean's Robotic Arm," and some others I may be forgetting. This adds to her overall bear motif - Mindy already regularly wears a bear hat, and when she finally gets to go to space, her helmet has bear ears on it.
Sunspot is dressed as a doctor, and I never understood why. Thinking about it more, it could represent how Sunspot cares for his friends, like doctors care for their patients? We saw that flashback in Space Camp, where Sunspot wrapped Jet in bandages after skinning his knee.
It could also be ironic - we all know that eating too much candy isn't good for you, and doctors all want us to be healthy. But Sunspot is dressed as a doctor on a holiday where people eat candy.
Jet, who we all know is a human-like alien, dresses up as a stereotypical green alien, which he thought was a giant cucumber costume. This highlights Jet's quirkiness, and since later on in the episode, he calls himself Cucumber, this adds to the vegetable theme naming that the rest of the Propulsion family follows. This alien costume also allows him to get away with saying he's from another planet.
And finally, Sean as his idol, Neil Armstrong. Much like Sydney, it makes sense that Sean would dress up as someone he idolizes. The staging in this particular shot is very purposeful; we all know that Neil Armstrong was the first person to walk on the moon, so having a giant moon in the sky in this scene is perfect.