Comic book
Thelonious is the executioner who works for Lord Farquaad. When Lord Farquaad returned from the dead as a ghost Thelonious was still loyal to him. Together they tortured the pigs and Pinocchio into telling them where Shrek, Fiona and Donkey were. After this information Thelonious goes on the hunt for Fiona and manage to kidnap her while being chased by Shrek and Donkey. But Thelonious manage to lure them into a cemetery where Lord Farquaad is waiting for them. In the meantime Thelonious ties Fiona to a raft and pushes it into the river leading to a waterfall but accidently gets on himself. They both end up drifting towards the cliff but Fiona manages to free herself from her bonds and after a short struggle where Thelonious is hit inbetween the legs with a wooden beam from the raft he falls from the raft into the water. As he tumbles off the cliff he managed to hang on onto a branch and catch fiona, but the weight is too much for the branch to handle and breaks off. Thelonious falls into the river below while Fiona is saved by Dragon.
Movie: Shrek
In the movie Thelonious is shown as an executioner working for Lord Farquaad where he tortures Gingy.