Here's what rhymes with happun.
done tion ton bun donne dun pun bn jun tonne tun one run son none sun won gun fun nun spun shun sion fon rien cen gon hun ven yean stun toucan naan begun undone fron outdone outrun overdone seisin spline redone overrun rerun cretonne misdone anyone everyone twentyone Words that almost rhyme with happun
tongue dem dumb dung bum dum tum tung chum tem bung some come young sum hung lung cum drum sung thumb comme gum rum hum plum rung stung wrung zum comm mum même num numb plumb kung sm trom sebum spume thrum yum from among become flung swung clung sprung slum slung strung succumb sacrum scum crumb glum swum frustum scrum strum benumb overcome overhung unsung rehung cerebrum breadcrumb simulacrum candelabrum mullein puncheon mustn fustian