Salling played Puck in the FOX series, which ran for six seasons from May 2009 to March 2015.
The actor posted the original message shortly after Kevin McHale, who played Artie in the series, retweeted stills from one of the show’s Christmas-themed episode.
Salling, who was arrested for possession of child pornography, died by suicide in 2018.
Morris, who played Brittany in the Fox series, told her Twitter followers that, when mourning her co-stars, it is “tough to have to act” like Salling didn’t exist.