Where does the Pardoner fit in?

For a detailed look at each of these characters, simply follow the link provided below to access Gradesaver's summary of the prologue. In this summary, you will find the order (from highest to lowest) or status of each of the pilgrims. I assume that this is what your question refers to as far as "fitting in." Chaucer's pilgrims represent the different rungs of English society. The summary will supply you with this information in order of importance. 

Travelling with the Summoner is a noble Pardoner, his friend and his companion (in what sense Chaucer intends the word 'compeer', meaning companion, nobody knows) and the last pilgrim-teller to be described. He sings loudly 'Come hither, love to me', and has hair as yellow as wax, which hangs like flaxen from his head. He carries a wallet full of pardons in his lap, brimful of pardons come from Rome. The Pardoner is sexually ambiguous - he has a thin, boyish voice, and the narrator wonders whether he is a 'geldyng or a mare' (a eunuch or a homosexual).