The Forever Handhold is the eventual result of several different fusions including: Trina Riffin (already fused with Mina Beff's nail-polish and glasses) and Nick Mallory (fused with a crusty Loaf of Bread). They were fused together in the episode "Kon-Fusion", as the result of several repeated attempts by Trina to fuse herself with Nick.
Their overall appearance includes Trina wearing Mina's glasses and blue nail polish, and Nick Mallory with his head replaced by a loaf of bread. The two are only fused by their hands.
After several failed attempts to fuse with Nick, which resulted in Trina getting fused with Mina's glasses and mermaid blue nail-polish, she finally succeeded in fusing with Nick, however unbeknownst to her Corey (as Corey Carrie) had dropped a loaf of bread onto the machine while Nick was touching it, causing Nick to get fused with the loaf of bread. This spells trouble for Trina who is severely allergic to bread crust and she immediately has an allergic reaction. However the prospect of being fused with her allergy forever proves too much and she goes into Diary Mode which is powerful enough to tear the fusion apart.