Callahan's rhymes with:
meehans, afghanistan's, afghanistans, afghans, alcan's, bedpans, businessman's, c-span's, caftans, caltrans, caravans, goodman's, greenspan's, intertrans, lifespans, lumberman's, meehans, pakistan's, rosecrans, rosenkrans, stockman's, tajikistan's, taliban's, talibans, tarzan's
Callahan's sounds like:
cackling, cajoling, calamine's, callens, calling, calmes, calming, calmness, calms, casualness, ceiling, ceilings, celanese, celnik, challenge, challenges, chileans, chilling, chiseling, chuckling, cieslinski, claiming, claims, clams, clancey, clancy, clancy's, clang, clank, clannish, clans, claunch, clawing, cleaning, cleanness, cleans, cleanse, clemans, clemence, clemency, clemens, clemmons, clemons, clench, clenches, climaco, climax, climaxes, climes, clinch, clinches, clines, clines's, cling, clings, clinic, clinic's, clinics, clinique, clink, clonch, clones, clones', cloning, clowning, clowns, cloying, clumsy, clung, clunk, clunks, clunky, coglianese, coleman's, colinas, colling, collinge, collings, collins, collins', collins's, collums, colonies, colonize, colonus, colony's, columns, colunga, cooling, coolness, cowling, cowling's, cowlings, cowlings', cowlings's, cullens, culling, cullins, cullum's, cwiklinski, cycling, cyclones