Little is known about their personalities since they appear sporadically throughout the series as comic relief, mainly due to encountering a few of Stitch's cousins who annoy or torture them in some manner. They love each other and enjoy having fun.
Charles is slightly arrogant about his job, often telling people he is a vice president. Mary's personality seems to be romantic often telling people they are on a honeymoon and trying to take in the sights. Charles seems out of shape as he couldn't keep up with Mary on a nature hike. He also enjoys taking pictures.
They first appeared in "Kixx", where they were seen walking on a nature trail and Charles threw his water bottle away, causing the water from it to trickle out and touch Kixx's pod, activating him. He later attacked the two.
In "Yaarp", they were taking pictures of Kauai and buying fruit from Mrs. Hasagawa before Yaarp blasted their eardrums with his megaphone, making them temporarily deaf. They later tried to buy a new camera at an electronics store, only for Yaarp to destroy the store. They then went to the same cave where Yaarp was hiding, while Pleakley went in to capture Yaarp. When Pleakley heard footsteps approaching, he turned on his vacuum sucker meant to capture Yaarp, but accidentally stole Charles and Mary's clothes as a result, though he gave them back. Later, when the cave collapsed, they ran out. They then went to a museum for peace and quiet before Gantu showed up and started attacking, causing them to complain to the mayor.
In "Drowsy", Drowsy put them to sleep by simply bleating.
In "Slick", Slick sold them a trophy which they used to keep the table they were eating on steady, but Lilo and Stitch bought it back.
In "Retro", the two were enjoying themselves on the beach as they were bathing before Retro was activated. He then turned their clothes, Mary's cell phone, and their car primitive.
In "Spats", Lilo tried inviting them to Jumba and Pleakley's Bed and Not Breakfast to help make money for Lilo, but they declined, saying it was too weird for them. Later, Spats zapped them with his argument-inducing ray and caused them to get into a fight, with Mary slapping Charles for getting too fresh with her and Charles saying it was their honeymoon. Later on, they watched the match between Suga Mama and Gantu and counted to ten, ending the belligerence between them as that was the cure to Spat's argument-inducing ray.
- As stated by executive producer Jess Winfield on his TV Tome Q&A thread, Charles and Mary are based on fellow executive producer Bobs Gannaway and his wife.