The Big Bang Theory is one of the best sitcoms of all time and, even though it ended seven years ago, it remains firmly in the public's consciousness. Personally, I wouldn't change much about the 12-season show, but there were plenty of creative alterations made before and while the series was airing. Certain scenes had to be cut for time, while other storylines simply didn’t get to see the light of day because of other reasons. Apparently, there was even a Sheldon scene that was discarded, and I think this would've been great.Brian Thomas Smith, who played Penny’s on-again-off-again boyfriend Zack in the beloved CBS sitcom, appeared on The Official Big Bang Theory Podcast, where he shared some more BTS stories about Big Bang. The actor made his debut as Zack at the end of Season 3 and returned for a few episodes in Season 4. Interestingly, Smith revealed there was a Season 4 episode he was supposed to appear in with a storyline involving Sheldon, but it didn't come to fruition for an unfortunate reason:Well, inside scoop here. There was another [Season 4, Episode 10] episode, or I guess it was earlier. They were bringing Zack back earlier in the season. I had rehearsed all week, and I got a call Sunday night. I think we tape on Tuesdays. And Kaley [Cuoco] broke her leg or hurt her leg [in] a horse accident. They're like, ‘She can't do the episode, so you're not going to be able to do the episode.’ Because that was the whole episode. And I was giving Sheldon advice on women in that episode. I vaguely remember it ‘cause we only had like a few days of rehearsals on it, but they had to write me out. And I was like, ‘This is my luck.’I can only imagine how chaotic Zack giving Sheldon advice about women would be. There's so much comedic potential in an exchange like that, and I'm sad it didn't happen. Still, I understand the reason for that, given Kaley Cuoco's injury. There was no point in having Smith in the episode if his on-screen love interest wasn’t going to be in the episode. Luckily, Smith was told he would eventually return to the show, and but writers had to find the right story for Zack. As the Bad Monkey alum explained, the right installment came along, and it's now a classic episode:So weeks went by [and] Bill Prady called me after the accident and was like, ‘Hey, just so you know, we love you. Your character's great. We want to bring you back. We're gonna figure out how to do that. So I kind of think that maybe the Justice League costume contest, might have been a Halloween costume contest, and they just pushed it back right to a New Year's Eve costume contest ‘cause I was in another episode. And it’s crazy, and then it got cut out.Season 4's "The Justice League Recombination" is a fun episode, and Zack is used in it perfectly. Yet the notion of Zack mentoring Sheldon on how to meet women is just too funny. However, the storyline not happening may have been for the better. As Smith went on to explain during his interview, he wasn't too keen on the scrapped scene for one reason:Yeah, it wasn't good. I think Zack was kind of mean, still. He was like kind of more like a womanizer type of guy. And I’m glad it was a little softer [in those] other episodes.Ultimately, Smith appeared in a total of 11 episodes throughout The Big Bang Theory’s run, and Zack became something of a fan-favorite character. He definitely caused some trouble for Penny and Leonard later in the series, but it was still fun to see what would happen. Just recently, Smith reprised Zack for a surprise cameo on Stuart Fails to Save the Universe, the newly minted spinoff series. That guest spot also reunited him with Cuoco. I sometimes wish Zack had been in more episodes of Big Bang, yet I'm still happy with the size of his role as it stands. And, who knows, maybe Zack will reappear on Stuart for more multiversal madness.Since The Big Bang Theory ran for 12 seasons, it’s likely that there are countless BTS stories that can be shared. Here's hoping we learn more like Smith's as time goes on, and fans can watch them all with an HBO Max subscription.