Allstar Seaworthy and Casey Kelp appeared to like each other throughout the course of the show. Rumor has it that they were even boyfriend and girlfriend. Contrary to popular belief, this is not the case, as their relationship changed between the first two seasons and the last two seasons.
Season 1 and Season 2
Although Allstar and Casey acted like a typical teenage couple, they mainly had big crushes on each other. In Allstar's case, this was evident in "The New Neighbors," although Casey danced with Tooter instead. It's possible she was playing hard-to-get with him. It wasn't until "Snorkdance" when it became obvious that Casey had a crush on Allstar. However, they were seen holding hands for a brief moment in "Hooked On a Feeling." Later on, the two went to dances together, and even on a few dates, despite what happened in "Allstar's Double Trouble," when Allstar scheduled two dates on the same night - one with Casey, and the other with Samantha.
During Season 1 and Season 2, it appeared that Casey liked Allstar the most - she even blushed when he complimented her (Learn to Love Your Snork)! Despite their strong relationship, Allstar and Casey never once kissed. The closest kissing scene only took place in Allstar's mind, regarding a worst case scenario involving Junior (Fine Fettered Friends). Still, the two snorks really liked and cared about each other, especially in the first two seasons.
Season 3 and Season 4
While Allstar and Casey remained close friends during the final two seasons, they appeared to act like just that. In fact, they were seeing less of each other in Season 4. On the other hand, Casey still appeared to have a crush on Allstar in Season 3 (A Farewell of Arms, Tooter Loves Tadah). Later on in the final season, Casey "got over" Allstar and began to show affection for Stevie, a popular football player at Snorkland High. At the same time, Allstar and Junior competed for a date with Celia, a popular Snorkland High cheerleader (Snorkerella). Beyond having crushes on other snorks, Allstar and Casey started arguing and bickering about the little things in life, which was rarely seen in the other seasons. For instance, they argued over who didn't have a "sense of adventure," let alone "who was supposed to pack the food" upon sneaking onto a pirate ship and Casey getting hungry in the process (Snork Ahoy). Much later on in the final season, Casey kissed Junior on the cheek after he gave her tickets to the local amusement park for her birthday (The Day They Fixed Junior Wetworth). In fact, she even danced with him in "I'll Be Senior." Of course, she may not have shown signs of affection for Junior.
It is possible that the writers could've avoided further continuation of the "Castar" pairing as a direct result of Dimmy's unexplained disappearance. When he left the show, Daffney did not have a partner she could have been paired with, and the writers simply did not want to focus solely on Allstar and Casey. If this had been the case, the final two seasons would have easily become Allstar and Casey Central, which might have caused the show the "jump the shark." Despite this, it was still hinted throughout Season 4 that the two snorks would someday be married to each other, even though these hints were only imaginitive fantasies (Allstar's Odyssey, The Story Circle). In fact, they even acted nervously excited to see each other in "Wish Or Wish Out," which also marked the final episode the two made an appearance together.
As a result of the relationship changes in between the first two seasons and the last two seasons, Allstar and Casey never progressed further into their relationship. In other words, the two never had any huge romantic scenes, unlike in other cartoons and anime. Still, the Allstar and Casey relationship is the most popular and the most memorable in "The Snorks."