If you don't know how to use a compressor, use Fruity Limiter's compressor. It's a lot easier to use than a traditional compressor, because you can see the waveform being compressed as you're doing it. You really should start experimenting with those -- compressors make kicks fatter and a lot of sounds beefier overall.
In Gator in the Tub, I think the main problem is that you don't really have any rising action going into the silent climax. The anti-climax thing works best if the music pushes into what you think is a big climax, and then after the anti-climax, comes back in HUGE.
You can make that rising action a large number of different ways. You can have the pitch rise somewhere, make the song faster (meaning have faster notes playing -- you'll hear that a lot in the drums), make the song louder (usually by adding more and more instruments, though a dramatic enough crescendo will work too). You can hear this at the very beginning of Alex S's "Party with Pinkie" -- the subdued intro enters, then the rising synth enters while Pinkie shouts something and the intro part kind of stutters in the background, before the filters disappear and the full song comes in LOUD.
Then, you can make the big entrance even louder and fuller. Maybe you could try doubling the bass and hard-panning the bass tracks left and right? Or adding side-chained pads, so that you can scarcely hear them but they fill out the sound? Just throwing some suggestions out there.
You can also do what Jeff said and apply a filter to the Bitspeek bit -- maybe a bandpass? I dunno. You should do something to add more contrast between that Bitspeek bit and the rest of the song around it, to make it more of an anticlimax and less of something that just happens. That'll certainly help a lot.
If you don't already, you should learn to EQ like Mike said. And if you don't already, make sure you pan everything a little to the left or right. It'll help things stick out more and make them less muddy.
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As for things clipping despite them being quiet, I can probably answer that. Soundgooderizer has a compressor built into it. =P If you lay compressors on the things with the biggest difference between peak and average volume (meaning, drum hits, etc.), you'll make it sound louder while actually making it quieter.
This article has a few pretty nifty things in it, so you might want to read through it. (Scroll down to the "Loudness Without Overcompression" section for the most relevant stuff.)
I'm kinda rambling here at this point. xD If anything I say doesn't make sense to you or is just flat-out wrong, feel free to ignore what I said.