The Three's Company star passed away from heart problems on 11 September, 2003, aged just 54, and as the world remembered the lives lost in America's 2001 terrorist attacks on Wednesday (11Sep13), two of his former co-stars took to Twitter.com to honour Ritter's memory too.
Cuoco, who played Ritter's daughter on U.S. sitcom 8 Simple Rules, marked the 9/11 atrocity first by writing, "neverforget forever standing tall!", before sharing a photo of the late actor with the caption, "Another person I will never ever forget".
She then uploaded another snap of the pair enjoying a rollercoaster ride and added, "One of my favorite memories. Riding California screamin (sic) w (with) johnritter ! (He screamed louder than me)".
Her trip down memory lane prompted pal Zegers to share his emotions with his Twitter fans as well and he posted a photo of himself and Cuoco laughing with Ritter, alongside the caption, "10 years ago today I lost a dear friend. One of the best men I have ever known. JohnRitter Rip".
Zegers and Ritter bonded while filming 1999 Tv movie It Came from the Sky.