Clarence is listed as the next kid Uncle Grandpa is going to help out.
At "The Grampies" short, Clarence, Sumo, Jeff and Belson are seen at the audience. In one scene, Belson shouts: "Who's in charge here?", and is knocked by a statuette. At the end they leave the centre like the other characters.
Clarence and Mary are shown in a TV-like window.
Pan mentions it when he talks about the revelations that Chris Savino, John Lasseter, and Nobuhiro Watsuki are sexual predators.
Jeff Randall appears in this crossover
Brought up in Stephen Neary's filmography.
EJ & Sue Randell are #6.
A crossover between Phineas and Ferb & Clarence is #9.
Everyone Watches "Adventure Time" is #10.
Clarence is #10.