Okay, here is some constructive feedback.
1. Messy: Once you start putting in too much dialogue and the graphics seem to float, it looks crappy, like you don't give a shit. If you put a lot of dialogue in the first panel to establish the size before doing the other panels, it seems to get around this. Or maybe the more experienced folks have a different way?
2. The running gag: The whole fire thing actually kind of works, though with more thought you could have added a bunch more puns.
3. Punctuation and grammar: Nothing makes a strip more crappy than when you can't spell, use proper contractions, etc. For example, the first line should read:
"Oh, Lisa! The fire in your eyes is amazing... You're so red hot!"
In other words... learn to write.
4. The punchline: He needs to do something that would make him spit when he talks. Or maybe she asks him to kiss him and he admits to being a drooler. Or something. There is some kind of "flow" lacking here.
Her "fuckin asshole" response is unfunny and unnecessary. Also, it is totally out character for a sweetly in-love flame-girl you established in the first two frames. Better to have her be a silent (dead?) pile of ashes...
Come to think of it, this whole thing would have worked better if they were having a romantic walk along the seashore, and a big wave comes in...
5. Narration: In this strip, the narration is redundant and diminishes the whole strip.
Well, that's my two cents. I'm not ripping you, just offering suggestions. If you follow this advice, you'll at least make strips that are funny to *me* (which doesn't count for much).
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...Trot and Cap'n Bill were free from anxiety and care. Button-Bright never worried about anything. The Scarecrow, not being able to sleep, looked out of the window and tried to count the stars.