Randy Cunningham is an average high-schooler who tries to fit in and be cool. There are many times where he tries doing risky things that could possibly get him into a lot of trouble, like busting Bash's party (House of 1,000 Boogers), spitting into a volcano (Monster Dump), and using the ninja powers to fix a science project (Dawn of the Driscoll). Often he forgets that his actions have consequences, which can accidentally or purposely result in major problems for himself and the people around him. As time goes on, though, he realizes when the situation is his fault, and takes responsiblity to fix it as much as possible. He always struggles to do what's right over his own desires, but he more often then not goes with the former. His sense of responsibility and sacrifice has increased throughout the series.
Though he is not very book-smart, Randy is very quick-witted in dealing with ninja situations, creating techniques, and facing normal life situations. Randy is also very good at riddles and puzzles as shown in The Tale of the Golden Doctors Note. Randy is also extremely skilled at games, much better than Howard is as seen in Weinerman Up.
He can be selfish, impatient, and a bit bossy, like his attitude with the Nomicon, but is a loyal friend and has a heart of a hero, the perfect ideals of a ninja. He also keeps his promises, for example, when Howard ask him to promise to stay in the locker for 10 seconds and he did even though Howard farts and closes the locker door. Howard can be troublesome and rude, but fortunately Randy is usually forgiving with Howard's actions. He can treat Howard unfairly or uncaringly at times, like saying Howard didn't have any understanding of having a duty, but he does his best to make it up, and works hard at balancing their friendship and his job as the ninja. Despite his negative qualities, Randy proves to be very valiant and upholds high morals, as seen in Ninja Camp when he refused to fight the other students and ran back to help a student get out of one of Mac Antfee's courses.
When Randy gained the mask and became the ninja, he thought it was butt-kicking and hitting, but discovers it is very hard fighting against robots and monsters, and soon gets used to it. He becomes quite serious with the job, which strains and sometimes nearly breaks his friendship with Howard. Ever since he became the ninja, he becomes more mature bit by bit in each episode with the proverbs he learns and understands from the Nomicon. It can take him awhile to figure out how to de-stank a monster or defeat a monster, but he claims and shows that he is doing his best to protect his school. In Ninja Camp Randy loses confidence and has doubts about being the right guy to be the ninja, but after encountering Antfee, he realizes that the Nomicon chose him because of his nobility and well-meaning heart and is was just a test for it.
Randy is seen to taunt his enemies and make sarcastic comments toward them. It is unknown what Randy's intentions are, but on several occassion he is seen angering the enemy in some way or maybe to make they more aggresive therefore making more mistake since robot make by Viceroy have emotion.He prefer to be fair even toward his enemies.