If you do decide to go skiuttlin', don't eat more than a box.
CCC is slang for coricidin cough and cold, a brand name cough preparation which contains DXM and (unfortunately) chlorpheniramine, an antihistamine.
The chlorphen (CPM) is an antihistamine like diphenhydramine can seriously fuck you up in high doses (deleriant-style). It can even kill you because it does not play well with the DXM and can induce serotonin syndrome. The general consensus is that because of the high levels of CPM in CCC there are much better products with DXM to abuse; that said, many people still do it because it's easily shoplifted availiable.
DXM FAQ suggests, probably rightly, that anyone who does CCC's stay at a second plateau dose or below, and ideally don't use them at all. The practical upshot is that you shouldn't eat more than one box.
If you want to get fucked up, go for it, but make sure to tell someone of your plans/get a sitter so if shit goes "up the river" so to speak you can get medical attention.