Jim Parsons and Kaley Cuoco are the unexpected duo you never knew you needed.

However, as the series progressed, the audience got to know a different side to both of them.

Their bond grew and, surprisingly, they even locked lips onscreen.

Jim Parsons and Kaley Cuoco smiling

While the smooch was obviously fictional, Cuoco and Parsons' genuine chemistry shone through.

Clearly, they were comfortable enough to sell it.

It was exactly what it should have been, and then, BAM, we were making out!"

Leonard watching Sheldon and Penny kiss

Notably, the two hit it off from the very start.

When Parsons shared his news with the crew, Cuoco found it especially difficult to cope.

Co-creator Chuck Lorre shared, “There was a lot of crying in the room.

Jim Parsons and Kaley Cuoco together

Kaley, in particular.”

According to executive producer Steve Holland, Cuoco’s disappointment was palpable the following day too.

“Kaley could barely make eye contact with Jim during the run-through,” he divulged.