Well, an ego trip in this story might be about the character's pursuit of things that boost their own ego. It could be achieving certain goals just for the sake of feeling superior or getting recognition. For example, if Dexter in the story is constantly trying to outdo others in his work not for the actual value of the work but just to satisfy his ego.
In this story, Dexter might be a character who is on an 'ego trip'. He could be someone who is ambitious, perhaps overly so. He might be constantly seeking validation, power, or recognition. His actions throughout the story could be a reflection of his egotistical nature. For instance, he may strive for success in his career or personal life not for the intrinsic value but to boost his own self - image and satisfy his ego. His character development could also be centered around learning to control or reevaluate his ego as the story progresses.
One possible plot could be that one of Dexter's female friends or a female character in the Dexter Laboratory world discovers she is pregnant. She might then turn to Dexter for help, thinking his scientific genius could assist in some way, like creating a device to monitor the baby's health in a unique way.
The Grim Reaper from 'The Grim Adventures of Billy & Mandy' could be an interesting addition. He could bring some dark humor and a different kind of magic to Dexter's world of science.
One idea could be Dexter crossing over with another smart character like Jimmy Neutron. They could compete in a science fair, leading to all kinds of wacky inventions and mishaps.
As I mentioned before, Dee Dee could be a likely candidate. She's always getting into Dexter's business, and a pregnancy could add an interesting layer to her character. It could show a more serious and responsible side of her as she prepares to be a mother.
It could be Dexter's teacher. If she got pregnant, it would add an interesting layer to the school environment in the Dexter Laboratory. The students, including Dexter, might be curious and try to understand what's going on. And she could be dealing with all the normal pregnancy stuff while also trying to teach her students, which could lead to some comical and heartwarming situations.
One idea could be that one of Dexter's female relatives, like his sister Dee Dee, accidentally gets pregnant. This could lead to chaos in the laboratory as Dexter tries to figure out how to deal with the situation while also keeping his scientific experiments running. Maybe he creates some sort of device to help with her pregnancy symptoms or to keep her out of his lab during her mood swings.
In the comics, Mantis has no relation to Ego. Their characters' storylines don't intersect in that way. Different comic arcs and story developments keep them separate.