If you haven't been picking these up as they're announced, Amazon decided to finally give you a way to get all 25 with one click over at their 25 Days of Free page (amazon.com) - scroll down past the days to find the checkable list and "Buy selected song" button.
Oh, one more thing - if you're GIFTING MP3s, Amazon says that you can get $2 off with the code GIVEMP3S. Details about THAT over here.
No offense, but I HATED the Star Guitar video. Though the length of the song probably didn't help. But, yes, "Bad Cover Version" is great, don't know how I could forget it since I just saw it last week.