While Giggles has dated several characters within the series, she has romantically interacted with Russell more than anyone else, with the exception of Cuddles. She has actually had the same amount of romantic interactions with Russell as with Cuddles, despite the latter being in considerably more episodes with her.
Not only has Giggles been on a total of three on-screen romantic dates with Russell (Sea of Love, You're Kraken Me Up, and Put Your Back Into It) but during these dates, she seems to be much more infatuated with him than on any of her three on-screen dates with Cuddles, constantly staring dreamingly at him. The only time this is broken is when he dives underwater in Sea of Love, preventing her from doing so.
During and before their dates, Russell seems to go to great lengths to make Giggles happy, such as diving down to a coral reef to get flowers for her in Sea of Love. Furthermore, in You're Kraken Me Up, he is so distracted during their date that he does not notice the Kraken. On a non-romantic note, he goes on a boating expedition with her in Snow Place to Go and is naturally horrified by her sudden death. However, it should be noted that he has been shown to be quite oblivious in unrelated episodes, like Something Fishy, in which he does not even seem to notice his helmet is his fishbowl until his piranha is right in front of his eye.