Bunnicula is a 2016 animated series produced by Warner Brothers and loosely based on the children's book series of the same name. The show revolves around Chester, a paranoid cat, Harold, a docile and dopey dog, and Bunnicula, a vampire rabbit, as they protect their owner Mina from all manner of supernatural evil in her new home in New Orleans.
Chester, Harold, and Bunnicula end up fused together when Harold unleashes an ancient Egyptian diamond that causes greed in whoever views it, as well as melding any life forms touching the diamond at the same time together. They manage to narrowly get the diamond away from an entranced Mina before she falls to the diamond's mutating effects.
The box containing the cursed diamond.
An ancient papyrus explains the diamond's curse.
This is the "curse" part.
As the fused pets fight over the diamond, it gets knocked away during the scuffle into a nearby chair...
...where Mina stumbles upon it, and falls under its power.
The pets quickly realize they have to get the diamond away from Mina while she's not touching it, or else she'll be drawn into the fusion.
Turning to berate Chester in her greedy paranoia takes her eyes off the diamond long enough for the diamond's mesmerism to wear off.
Harold frees Bunnicula by shutting the diamond back into the box.