Channel 4's I Hate You has a celebrity cameo you definitely missed

I Hate You's offbeat title sequence sees Reynolds and Saint busting moves in a neon-lit, disco-type setting, only for the pair to be unsettled as a curtain is pulled back to reveal a white horse, who mutters, "I hate you." (Yes, the horse speaks.)

And voicing the horse? None other than Peter Serafinowicz, in an uncredited contribution to the series. (Fans of Popper's work will know that he and Serafinowicz co-created, co-wrote and starred in the acclaimed BBC comedy Look Around You in the early 2000s.

"I was so scared about it, because Melissa can dance and I cannot dance," Reynolds told RadioTimes.com about filming the titles. "It was really hard for me to learn choreography because that part of my brain does not work. But Melissa was like... boom, boom, boom! She was so good."

As for their co-star, the horse, his name is Rusty and he was actually present on-set, though ultimately had to be shot separately and digitally inserted into the sequence after getting spooked by the curtain.

"That horse has worked more than I have," said Reynolds. "He's, like, a celebrity horse, so was chill with the music and the lights. In the lead-up to shooting it, they played Rusty the music quite a lot so he got used to it.

"He just didn't like the sudden-ness of the curtains opening. He had to be in one spot and the curtains would open and he would move, so eventually, they had to just shoot him separately and then CGI him in it."

I Hate You hinges on the relationship between Charlie (Reynolds) and Becca (Saint) and the chemistry between the pair, with one or both of the two leads appearing in almost every scene. Finding the right pairing was "a long process", according to Saint, with Reynolds being cast first and then doing "a lot of chemistry reads" with different actors.

"They cast Tanya in November 2021 and then I think there was a four-month gap between casting her and casting me," Saint recalled. "When I got the job, Robert was like, 'We've seen over 200 girls.'

"I know that Tanya had to do chemistry reads for quite a few other people before I came to do mine."

Reynolds and Saint, though, "instantly got along and had fun in the room" when reading together – but once they were both hired, the biggest challenge came in learning the zippy, rapid-fire, back-and-forth dialogue for which Popper is known and will immediately feel familiar to fans of Friday Night Dinner.

"It was so much to learn," said Reynolds. "Neither of us had done anything before where we'd been the leads in a show and where the show is mostly just two people. We were in every day and had so much dialogue. I've never done that before, so I've never really struggled with learning lines before – because I've never really had that many!

"But with this, having so many lines, that was probably the hardest bit, because we'd go home at the end of the day and have, like, 14 pages to learn for the next day because it was just too much to learn all in one go.

"It'd be first thing in the morning and we'd be half asleep at 5:30am or whatever time we got in, doing the lines to each other, just trying to know them as well as we could, so we could be as quick as we needed to be, because Robert's constant note throughout filming was 'Can you do it again, but just faster? More pace, more pace!' – just constantly."

I Hate You airs on Channel 4 from 13th October at 10pm and all episodes are available on All 4 now.

Check out more of our Comedy coverage or visit our TV Guide to see what's on tonight.

The latest issue of Radio Times magazine is on sale now – subscribe now and get the next 12 issues for only £1. For more from the biggest stars in TV, listen to the Radio Times podcast with Jane Garvey.