Joe Manganiello was another major name to appear on The Big Bang Theory during the show's final season. Fans had a blast with the cameo and his scenes, however, fans weren't particularly pleased with a certain Leonard line after meeting Joe Manganiello. Leonard discussed his time alongside the actor with Penny, and fans noticed a certain plothole, we'll reveal what that was and why the moment was viewed as a letdown.

Speaking of guest stars, we'll also take a closer look at one Johnny Galecki himself went out of his way to approach at an event, without even knowing if the iconic actor had ever watched the show. Galecki had a vision for the actor on the series, and it seems like the approach worked. Let's take a look at how it all went down, and more.

Johnny Galecki Had Major Input On A Specific Big Bang Theory Guest Star

The Big Bang Theory had plenty of memorable guest stars, but it seems like Johnny Galecki had a particular vision for the role of his father on the show. Looking back, Johnny couldn't help but laugh at the way he approached guest star Judd Hirsch. Galecki had invited the actor on without even knowing if he had ever watched the show or for that matter, knew who Galecki was.

Hirsch would actually confirm the story, though he was ultimately pleased with the offer and happy to join for the cameo.

The actor revealed, "He just sort of cornered me one day. We were at a celebration of Jamie Burrows' 1,000th show, and at that celebration - since he did the pilots of all the shows that we know, he did The Big Bang Theory, believe it or not - and Johnny Galecki just came over to me on the stage when it was all over. . . . 'Would you like to be my father?"

"I go, 'Why not? Why not?' And Johnny said, 'I never had a father on the show and I always thought that I was like you.' And I'm thinking, 'Where?' [laughs] He actually thought that, in real life, that he could have come from someone like me."

Hirsch was yet another big name to join the show.

Another particular episode featured a star-studded cast, though fans weren't happy with a particular line issued by Leonard.

Big Bang Fans Could Not Understand How Leonard Didn't Know Joe Manganiello Given His Roles In Superhero Films

During the show's final season, Leonard would take part in a game alongside Joe Manganiello, Kevin Smith, William Shatner, and Kareem Abdul Jabbar, who all played guest-staring roles.

Although fans appreciated the guest stars, a certain Leonard line did not sit well with the fans. Talking to Penny about who he was with, Leonard didn't have much of an idea of who Joe Manganiello was. "That guy that played the werewolf on True Blood, he was there." Penny responds, "From Magic Mike!?" Only for Leonard to respond, "what's that."

Fans weren't impressed with the moment given that Manganiello has plenty of credits in superhero films that someone of Leonard's stature should be familiar with.

One fan writes, "Surely if Leonard is such a geek, he'd know Joe Manganiello from the original Spider-Man trilogy."

"Also from justice league (deathstroke)," another fan notes.

Despite the hiccup, the cameo was still enjoyed by fans, and it turned out to be a memorable episode.

William Shatner Also Appeared On The Star-Studded Episode, But Had Initially Turned Down The Show's Offer

Among the guest stars during the episode included William Shatner. As it turns out, getting Shatner on the series took an effort behind the scenes. He had initially rejected the show's offer given that he wasn't into the plot creatively and what they had in mind for his cameo.

However, according to The Big Bang Theory showrunner Steve Holland, Shatner was more open to appearing down the road given his growing relationship with Kaley Cuoco.

"I think what changed going into the final season is that he knows [series co-star] Kaley [Cuoco] from doing [Priceline] commercials together and they're friendly," he said. "When I got on the phone, one of the things he asked was, 'Will I get to play a scene with Kaley?'"

As expected, Shatner was a complete pro during his time on the show. "It shouldn't be surprising that he's good — he's been doing this a long time, especially playing himself — and it was really interesting to watch him work," Holland revealed.

"He would play a scene for a couple of takes until he found a delivery he liked and then really locked into it. He'd play around with a line a little bit and find what felt right to him and lock into that."

Among the top cameos especially given all the Star Trek references.