Seth MacFarlane pulled off an 'insane' transformation into Bill Clinton on the TV series Ted, with fans asking: 'It has to be some kind of special effects, right?'

The show is a prequel to Seth's movie series of the same name, following a younger John Bennett and his foul-mouthed talking teddy bear.

Family Guy creator Seth reprises his voice role as Ted, in addition to being an executive producer. 

And in the fifth episode of season two, viewers were stunned by an apparent cameo from former President Bill Clinton.

One wrote on X: 'They had Bill Clinton appear in an episode, and I can't tell if it's a lookalike or some sort of CG or AI because he looks EXACTLY like the real thing. 

'It's gotta be some sort of special effect, right?'

Another said: 'Am I looking at a.i Bill Clinton in Ted.'

While a third asked: 'Why is Bill Clinton in Ted?'

As it turns out, it is actually Seth himself doing an impression of Bill Clinton, who was in office during the show's timeline.

The team created a digital mask using deepfake technologies to help Seth pull off the performance.

He revealed to AP News: 'We filmed this a year and a half ago, that's how long it takes us to do the CGI. 

'It's an interesting example of how AI can be used as a tool and not necessarily trample on the art that the rest of the industry is doing.

'We tried prosthetics, we tried traditional CGI, and everything just looked terrifying. So we just said, "To hell with it, let's try AI". It worked, it was the only way to look like Bill Clinton.'

One viewer backed the idea, pointing out how convincing it had been: 'It's actually insane how much Seth looks like Bill Clinton here. 

'You could have told me they invented a time machine and kidnapped him from 1995, and I would have believed you.'