falsify (falz ee' fy) - multiply (episode 440303)
familler (fa miller') - familiar (episode 440104)
fanatics (fuh nat' ikz) - fanatical (episode 440522)
far (far') - for (numerous episodes)
farred (farr' duh) - fired (numerous episodes)
farrin (far' un) - firing (episode 441009)
favorance (fay vor unz') - favor (verb) (episode 440614)
favorite (fay vor rite') - favorite (episode 440703)
feerocious (fee' row shush) - ferocious (episode 4405216)
felled (feld') - fell (episode 350709)
fer (fur') - far or for (numerous episodes)
fergive (fur giv') - forgive (numerous episodes)
ferrin (fair' un) - foreign (episode 350405)
fevers (fee' vurz) - fever (episode 450221)
ficaticious (fic a tish' us) - ficticious (numerous episodes)
figgers (fig' urz) - figures (episode 350325)
filum (fil' um) - film (numerous episodes)
final (fie' nul) - finally (numerous episodes) [also: final (episode 440601)]
finance (fy' nanz) - fiancé (episode 450326)
finality (fie na'l it ee) - final (episode 440522)
fit (fit') - fought (episode 350107)
flat-footed (flat' foot' ed) - honestly (numerous episodes)
flewed (flewd') - flew (episode 350606)
flied (fly duh') - flew or flown (episode 44114)
Floridy (flor' id ee) - Florida (episode 440622)
flower (flow' urz) - flour (spelled)
fluence (floo enz') - influence (episode 400228)
flywers (fly' urz) - flowers (episode 450321)
folies (foe' leez) - follies (episode 350624)
foolishest (fool ish est') - most follish (episode 350829)
foots (footz') - feet (episode 440706)
forgave (for gave') - forgiven (450528)
formyla (form ee' luh) - foruma (episode 440215)
fortunes (for' chunes) - fortune (episode 440105)
founds (fowndz') - found (episode 441122)
founting (fown' ting) - fountain (episode 440622)
founty pen (fown tee' pen') - fountain pen (episode 440313)
Francisco (fran sis' koe) - Slang for 'Frisco (San Francisco)
Fran Sancisco (fran' san sisko') - San Francisco (episode 440214)
friendships (frend' shipz) - friendship (numerous episodes)
freshmans (fresh' minz) - freshman (episode 430920)
freshments (fresh' muntz) - refreshments (episode 350725)
Front Commander - made-up Naval rank (according to Lum, [paraphrasing] this is what you work for after you become a Real Admiral)
full-fledgling (fool' fledge' ling) - full-fledged (episode 440303)