The full version of the 1991 version with Scott, Sean, Barry, and Elliott.
There was ONE EPISODE with the theme song sung in full! It's "Happy Happy Troy Troy" and aired in 1993. Producer Dana Calderwood and some of his staff made a cameo as the villains who tied up Rockapella in the alley and "sang" the first part of the song, only to be tied up in later by Rockapella, who then sang the rest of the full song.