A bonding agent.
You can tuna piano but you can't piano a tuna! Don't ask me about the bucket of glue though... I've been stuck there for a while
You can tuna piano, but you can't piano tuna.
Anyone can tuna piano, but nobody can piano a tuna!
someone flipped it.
Bond: my PPK Money Penny: 'K
They can't bond with each other, no matter how hard they try.