Each season of Total drama has the main protagonists and one or two antagonists. It seems like there are filler characters that are just there. Because the main protagonists are the ones that return for another season. I figured out the filler characters from at least every season. There are some filler episodes.Here is my list of filler characters.
Pre- TDWT Noah
Pre- TDWT Ezekiel
Dave(there to just start drama)
Ella (there to show that Sugar was the season's villian)
TDWT Bridgette (there to show that Alejandro is the season's villian,a song in an episode and to add another contestant on team opposite of victory.)
Pretty much all of team opposite of victory except Ezekiel and DJ.