well, without knowing the cartoon you're talking about, it's hard to be specific, but you could look at:
- framing
- colour
- vectors
- line
- parody and satire (all cartoons are satirical in nature)
- hyperbole
- what actual words and how they're written
- language techniques in the written words
- intertextuality
there are other techniques that may be applicable, but it would be too long a list without some idea of what the cartoon you're talking about is.