humor

Interpretation: note the humor: Bloom putting down Mulligan while Stephen is literally wearing the shoes Mulligan gave him.. Thus if Bloom were "in [Stephen's] shoes" he'd be in those of Mulligan.

This narrates Bloom farting just a little bit ("Pprrp. Fff. Oo."), making sure the lady behind him didn't hear, and deciding to hold it in until the "Kran kran kran" of the upcoming tram offers "a good oppor"[tunity] to cover it with a loud noise. When it brakes ("Krraaaaaaa") he lets loose ("PPrrrpprrfffprrff"). This chapter, "Sirens," is the music chapter, so ending it with Bloom's windy instrument is not only funny but thematically appropriate.

"Come" is the essential pun in Ulysses: a noun, a verb: not only motion, but also orgasm and semen. This is the last instance of "come" used for orgasm, although there are eight more instances to come in the Penelope episode. Recognition of Joyce's pun is part of the fun in the novel.