The Real Person Who Inspired Leonard on The Big Bang Theory (And It's Not Who You Think)

As it turns out, the neurotic, awkward physicist on The Big Bang Theory was inspired by a very real person from Galecki's childhood — and a meerkat.

In The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series, Galecki told author Jessica Radloff that Leonard's mannerisms were based on his childhood friend Tommy Loeper:

"I grew up with Tommy from the age of seven. He had a specific way about him that never left me. I still remember his posture. Leonard was really Tommy Loeper, but I also based the posture and physicality on a meerkat. That's where the clasped hands came from."

Galecki has a habit of blending animal traits into his characters, saying he studies animal photos because they're free of "persona or falseness." A photo of three meerkats standing together with their paws clasped? That became Leonard.

He also admitted to borrowing from Judd Hirsch's character Alex Reiger in Taxi — not in performance style, but in function:

"As far as the purpose that the character would serve. And that's why I asked Judd if he'd be willing to play my dad in the season 9 finale."

Executive producer Steve Molaro noticed the physical transformation:

"If you really look, Leonard carries his body differently than Johnny. It was fascinating to watch."

But Galecki didn't stop at posture. He went as far as giving Leonard his own distinct smell. Co-star Kaley Cuoco recalled:

"Johnny also had a very specific smell that was just for Leonard. I don't think he'll ever spray that cologne again, but because I was around him so much, I knew that smell. He was very superstitious about that."

Galecki explained the inspiration came from Tommy Loeper's apartment building in Chicago, which smelled of dry cleaning fumes from the ventilation system. He found a cologne called Clean, which mimicked that scent: "Over the years, I went through like two bottles of it."

This led to one on-set emergency when Galecki forgot to spray the cologne before a scene and had an assistant director retrieve it mid-shoot:

"I had to have it. And I know that makes me sound like a crazy person, which is somewhat true, but everyone's process is what it is."

He even gave the last of the cologne to Chuck Lorre — though Lorre admitted he has no idea where it ended up: "That cologne might be sitting in a medicine cabinet somewhere. I stopped using cologne a long time ago."

Galecki's connection to Leonard wasn't immediate, but one scene hit surprisingly close to home. In the first season's Halloween episode The Middle-Earth Paradigm, Leonard gets physically humiliated by Penny's ex-boyfriend Kurt — a moment that made Galecki cry after filming:

"It really dug up some old schoolyard stuff for me. It didn't happen all week during rehearsal; it was only when we shot it that it really hit home — in a good way, though, because I had a way into Leonard and really began to understand him."

That was also the episode where Penny kissed Leonard for the first time, albeit while crying over her bad dating history.

Reflecting on his time with the character, Galecki said: "I hope I have carried some of Leonard's traits like that with me in real life. When you love a character, there's certain things you want to retain from them on a cellular level."

The Big Bang Theory is streaming now on Max.