First thing I thought of was this old commercial, but that's probably not what you're referring to. :-D
"Charlie" is also the name given to "the enemy" in the US Army.
Maybe this is the source of the spy-fiction* usage of 'Charlie's Indians' to mean "CIA".
*At least, that's the only place I've seen it used.
Likewise, the abbreviation "CIA" would be pronounced "Charlie-India-Alpha" in the NATO phonetic alphabet, which is probably where "Charlie's Indians" evolved from.