Cloudy failed to join BFDI, BFDIA, and IDFB (has only joined BFB so far) so interactions between Cloudy and other characters are limited.
Bell was attached to Cloudy when Fanny blew them away when they failed to join BFDI with 4 votes.
Status: Minor Friends
Bomby and Coiny
In No More Snow!, after Coiny and Bomby helping Pin to get out, Cloudy and Lightning appeared over the tree and struck the tree. Coiny and Bomby were running away and screaming.
Status: Minor Enemies
Fanny blew away Cloudy and Bell when the Announcer said that Cloudy and Bell only got 4 votes to join BFDI, thus failed to join.
In Getting Teardrop to Talk, after Leafy's confrontation with Fries, she offers to befriend Gaty, Nickel, and Cloudy. Nickel and Cloudy accepted, with Cloudy saying that "it's good to collect as many friends as possible." Cloudy later gets prompted by Leafy to join her team and accepts. However, in Lick Your Way to Freedom, Leafy starts trying to manage Cloudy, such as assigning him a job, which he doesn't like.
Cloudy and Lightning have never shown direct interaction, but Lightning is summoned when Cloudy is angry. One instance of this is when Lightning strikes down a tree that collapsed on Pin in No More Snow!.