The Rookie star Nathan Fillion loves to crack jokes while on set. and he didn't hesitate to do so about his fellow cast mate Eric Winter.

On June 22, Nathan went on the ABC series' official Instagram to give fans a look at behind the scenes of filming the hit procedural drama. Uploading a video in which he dressed as his character John Nolan, Nathan sat down at one of the show's desks to answer a question that fans apparently contemplate while watching episodes of the show.

"Some of you are wondering when you see me writing on my little notepad as John Nolan in the role call room ... what am I writing?" he said in the clip. "Well, that's an excellent question. Let's take a look."

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As he opened the well-used prop on camera, Nathan revealed the contents of the notebook his character often has in hand. Among pages of doodles and lines, Nathan explained that the notes served as indicators of which episode was being filmed.

But eventually he flipped to the last page, which had a message regarding his fellow actor. "Have Eric Winter fired for making that joke about my hair," it read. This led him to jest about a personal request from viewers.

'The Rookie'

'The Rookie'

'The Rookie'

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"Maybe don't tell Eric you saw that," he joked before the video cut off.

While Eric didn't reply with his own response to Nathan's surprise call out, this didn't stop The Rookie fans from thinking this could be a teaser for season 6.

"Jajajajajajaja not me pausing to read it thinking it was a spoiler for next season 😂," one person wrote on Instagram. "ARE THEY FILMING SEASON 6!?" another added. " 😂😂😂😂 we need more episodes @nathanfillion," a different follower commented.

Well, it looks like it's now Eric's turn to follow up on the shots Nathan hilariously fired. And if he wants to drop any clues about when season 6 will air, folks would definitely not miss them.