Two interesting joke chord sequences designed to confound the parser.
|: I7 IV7 IIo7 bIII7 IIm7 V7 bV7 bVo7 IIIm7 VI7 IIm7 bII7 :|
This can be analysed as one long cadence. Not only that, but the cadence never resolves.
A dominant interpretation can be applied to each chord and is, in fact, highly plausible, since they're all seven chords of some sort. The dim7s are all true diminished chords (i.e. rooted a major third below their apparent root). The only other substitution is the tritone substitution.
The sequence's roots in this interpretation proceed in fifths (all the way round the circle, for circle fans). This means the end of the sequence joins up again with the beginning.
Here are the true roots
I7 IV7 IIo7 bIII7 IIm7 V7 bV7 bVo7 IIIm7 VI7 IIm7 bII7 I IV bVII bIII bVI bII bV VII III VI II V
Double Eternal Cadence
|: I7 IV7 bVIIm7 VI7 IIm7 V7 :|
This works in the same way, but the entirely dominant interpretation means that the second half (last three chords) are tritone substitutes. When you repeat, the initial I7 must therefore also be a tritone substitute if it is to join up the cadence. Of course, when you get halfway through you switch back to unsubstituted chords again.
This also forms an unending cadence, but only gets all the way round the equal temperament circle of fifths once you've played it twice. Every other time, the interpretation of the chords is reversed: first three substituted, last three not.
Here it is with true roots:
I7 IV7 bVIIm7 VI7 IIm7 V7 I7 IV7 bVIIm7 VI7 IIm7 V7 I IV bVII bIII bVI bII bV VII III VI II V