Rob McElhenney celebrates Danny Devito's 80th birthday with incredible message about co-star

Rob McElhenney celebrated Danny Devito’s 80^th birthday with an incredible message about him.

The pair star alongside each other in popular US sitcom It’s Always Sunny in Philadelphia. Written by the co-owner of Wrexham A.F.C, Devito has played Frank Reynolds since the second season of the now 16-season long show (with two more definitely set to come).

And of course, with a legend status like his, birthday wishes flooded in for the 80-year-old on Sunday (17 November) from all sorts of Hollywood stars and famous faces.

McElhenney’s was pretty sweet too, even if some did panic when they first saw it - “You can’t just post a pic like this man I had a heart attack,” one user wrote in the comments.

Danny Devito has been in Always Sunny since the second season (Gilbert Carrasquillo/GC Images)

The actor shared a solo snap of Devito to Instagram as he wrote in the caption: “This man was born 80 years ago today. He could still drink you under the table. He could still make you laugh harder than anyone you’ve ever met.

“He could still make you feel like you’re the only person in the room. He could still give you the best advice you’ve ever gotten and make you feel loved no matter what.

“He’s an American treasure. There is only one @dannydevito Happy Birthday!!!!”

And initially panicked users quickly commented to say: “Rob scared me last year, so I made a mental note that Danny’s birthday is in November, and he still got me this year.”

Others piled on the celebrations as they shared their favourite Frank Reynolds and Devito quotes and memes.

“National Treasure!” others agreed as they called the star a ‘hero’.

Olson, Devito and McElhenney (Jeff Fusco/Getty Images)

Fellow Always Sunny star Kaitlin Olson, who plays Dee Reynolds, also shared a birthday tribute: “Happy birthday to my favourite (rum) ham. Danny DeVito is everything you want him to be. Lights up every room, makes sure everyone is taken care of, gives his whole heart to everything and everyone he loves. Here’s to 80 more. I wouldn’t put it past him.”

Mary Elizabeth Ellis also wrote: “Happy Birthday to one of the most generous, fun loving, funny, kind, smart, lovely people I know.

"I'm so grateful to have known and loved you (and your wonderful family) for 20 years! You have enriched my life in endless ways. Gratitude doesn't cover it all, but it's a great place to start. Happy Birthday, Danny! #dannydevito I love you a lot."