Season 1 and Season 2
Dimmy and Daffney have appeared to have crushes on each other during the first two seasons. However, it has been more obvious that Daffney likes Dimmy more than Dimmy likes her. In Vandal Scandal, he seemed a little surprised that Daffney wanted to walk him home. But he did indeed portray to have a crush on her, as he blushed after she tied him to a rope in A Snorking We Will Go. Some of their more romantic moments include the episodes Snorkymania, Snork Marks the Spot, and Hooked On a Feeling. However, Dimmy does sometimes care more about food than her (Snorkdance). In fact, Daffney gets mad at him for not appreciating her, so she takes Jojo to the Debutante Ball instead. Dimmy proves to her he can be just like Jojo, so although he ruins the party, Daffney takes him back (Me JoJo, You Daffney). However, Dimmy has appeared to like other girls, such as Serena in The Littlest Mermaid.
So What Happened After Dimmy Disappeared?
When Dimmy disappeared in Season 3, not much had been heard of about his life, and it is shown throughout the later seasons that Daffney sort of likes Junior. However, there have been times this wasn't quite as obvious, such as in Rhyme and Punishment and The Day They Fixed Junior Wetworth.
Despite Dimmy and Daffney not getting as far into the "relationship mode" as Allstar and Casey did during the course of the show, they are still considered a very popular couple in the series.