Shut Up was used in the earlier seasons of the show. Later on they used, Be Quiet, Stop Talking, And Shut It
In the early seasons profanity such as crap, piss, hell and frick are very constant appearing in nearly every episode but the swearing dies down as the show moves along.
Cartoon Network and Hulu have censored seasons 1-3 for example in the debut episode titled "The Power" the original unedited version of the episode has Rigby saying "how in the H are we going to fix this S" however the Cartoon Network and Hulu versions of the show replace that line with "how in the heck are we going to fix this stuff" the unedited versions of each of the episodes are available on the home media releases of Regular Show.
Mild language and crude humor.
"Crap", "freakin", "pissed off", "turds", "balls", "heck", "hot" and similar language are used throughout. As of season 3, "crap" and "pissed" have not appeared in any episode.
in later airings, all instances of "pissed" were replaced by "ticked"
In three episodes ("Just Set Up the Chairs", "The Unicorns Have Got to Go" and "See You There"), "what the hell" is said.
Mild words like "sucks", "jerk", "blows", "idiot" and "screwed" are used. In the finale episode "My God" is used.