HMMMMM...Mixed Metaphor or Double Antandre.....that is a conundrum.
I think ironic is if you were to choke to death on a life saver.
Mixed Metaphor = "If we can hit that bullseye then the rest of the dominoes will fall like a house of cards... Checkmate."
A double entendre is a figure of speech in which a spoken phrase is devised to be understood in either of two ways. Often the first (more obvious) meaning is straightforward, while the second meaning is less so: often risqué, inappropriate, or ironic.
The Oxford English Dictionary defines a double entendre as especially being used to "convey an indelicate meaning". It is often used to express potentially offensive opinions without the risks of explicitly doing so.
A double entendre may exploit puns to convey the second meaning. Double entendres tend to rely more on multiple meanings of words, or different interpretations of the same primary meaning; they often exploit ambiguity and may be used to introduce it deliberately in a text.
Sometimes using a homophone (i.e. a different spelling that yields the same pronunciation) can sometimes be used as a pun as well as a "double entendre" of the subject.
I think the coupling of "the first one makes the other one look better" with "Nothing says drink Dr Pepper like a can of Mr Pibb" would kinda fit double entendre...not literally but in the way it is presented...even more deeply ironic than literally ironic.
Don't confuse homophone with bananaphone...
http://www.youtube.com/watch?v=Csf15kwNn6I&feature=related
"bananas are like the opposite of traffic lights...
Green means Stop!~don't eat that banana yet!
Yellow means GO... go ahead and eat that banana...
Red... where the hell did you get that banana?"- Mitch Hedberg