Thursday's (February 6 2020) episode saw The Royle Family actor, 39, arrive to replace former lead Ardal O'Hanlon, who played DI Jack Mooney since 2013.
Viewers were torn over whether or not Ralf is a worthy replacement, with some calling him "perfect" for the series and others fearing he might be the death knell for the long-running show.
Reacting on Twitter, one viewer said: "Was very sad that Ardal left but brilliant casting Ralf Little, he's ace! #deathinparadise."
Someone else tweeted: "Another entertaining, light-hearted episode of #deathinparadise Ralf Little fits right in. Enjoy it for what it is, simple good fun."
A third put: "Ralf Little makes such a good detective #DeathInParadise."
"Couldn't have chosen better than Ralf Little to take the lead in #deathinparadise," said a fourth.
Another wrote: "Well, Ralf gets my vote. Perfect replacement inspector. Brings his own quirks to the role. Looking forward to following his journey #DeathInParadise."
"Ralf Little is actually hilarious in #DeathinParadise," tweeted another fan.
But some weren't keen on Ralf joining the cast, as one viewer tweeted: "Not liking Ralf Little, but love Steve Pemberton so much I'm forcing myself to watch it. Wish they could bring back Humphrey. #deathinparadise."
"Just when you thought #deathinparadise couldn't get any worse... Ralf Little is the new DI," said another, alongside sad-face and laughing-crying emojis.
A third predicted his casting could be the end of Death in Paradise, writing: "Don't think #deathinparadise will survive Ralf Little. Thanks BBC another top prog down the toilet."
"#DeathInParadise is one of those very few programmes that the other half watches that I can tolerate," said another, adding, "But the introduction of Ralf Little will test that tolerance."
Prior to his Death in Paradise debut, Ralf joked that even his mum feared he might ruin the show.
In a chat with Radio Times magazine, he said she asked him, "But what if no one likes you and they stop watching it?"
- Death in Paradise series nine continues on Thursday (February 13 2020) at 9pm on BBC One
What did you think of Ralf's debut? Leave us a comment on our Facebook page @EntertainmentDailyFix and let us know what you think.