From Latin CATTUS 

ESSERE AGILE COME UN GATTO — to be as agile as a cat

ESSERE IN 4 GATTI —  To be 4 cats, to be very few people

‘C’erano solo 4 gatti allo spettacolo’- ‘There were only a few ppl at the show’

ESSERE DEL GATTO — to be ‘of the cat’, to be in a bad situation, problematic, almost hopeless

‘Siamo del gatto’ - ‘We’re screwed’

ESSERE COME IL GATTO E LA VOLPE — to be like the cat and the fox from Collodi’s Pinocchio, to be partners in crime

‘Alessio e Massimo: eccoli lì, sempre a combinarne una’ - ‘ Alessio and Massimo, here they are: always confabulating something’ 

QUANDO IL GATTO NON C’È I TOPI BALLANO — When the cat isn’t home, the mice dance

‘Come ci divertiamo ora che il capo and in vacanza! Quando il gatto non c’è…' -  ‘We have so much fun now that our boss is on vacation! when the cat isn’t home…’

FARE LA GATTA MORTA — To play the dead  female cat, to be super flirty!! or pretending to be sweet and masking the real nature. Refers to cats playing dead when trying to get their prey

‘Guarda guarda come fa la gatta morta!! Lascia qualcosa per noi!’ - ‘Look how she’s flirting!! Leave something for us!’

NON DIRE GATTO FINO A CHE NON CE L’HAI NEL SACCO — Don’t say cat until it’s on you sack! Don’t celebrate too soon

AVERE UNA BELLA GATTA DA PELARE — To have a big cat to shave, to have a big problem to solve

GATTA CI COVA! — the cat is nursing something, like a chicken is brooding the eggs, something is happening behind closed door 

‘Non mi fido di quei due: qui gatta ci cova’ - ‘ I don’t trust those 2… something is boiling in the pot’

From Latin MUSCA = FLY

ACCHIAPPARE LE MOSCHE - to catch flies, to do a useless job

"Cosa devo fare?" "Prendi una mosca e falla ballare“ - "What can I do?’ ‘Get a fly and dance with her’”

ESSERE NOIOSO/ FASTIDIOSO COME UNA MOSCA, to be annoying as a fly

‘Giovanni è fastidioso come una mosca: ha sempre da criticare!" - "Giovanni is as annoying as a fly: he’s always criticizing’

STARE A GUARDARE LE MOSCHE CHE VOLANO, to stare at flying flies, being distracted, not doing anything 

“E tu? che fai? Stai a guardare le mosche che volano?" - "And you, what are you doing? looking at flies?”

NON SI SENTE VOLARE UNA MOSCA, you can’t even hear a fly flying for how much silence there is

‘Da quando il professore si è arrabbiato, non si sente volare una mosca’ - ‘Since the teacher got upset, you can’t hear a fly’

ZITTO E MOSCA! Shut up as a fly!

AVERE PAURA DI UNA MOSCA, to be afraid of a fly, of nothing

FARE DI UNA MOSCA UN ELEFANTE, to make an elephant out of a fly, to make a big deal out of nothing

‘Hai fatto di una mosca un elefante! E’ stato solo un fraintendimento!’ - ‘You made an elephant out of a fly! It was just a misunderstanding!’

RESTARE CON UN PUGNO DI MOSCHE, to be left with an handful of flies, with nothing 

FAR VENIRE LA MOSCA AL NASO, to get the fly on the nose, to irritate somebody

‘Quando Giacomo mi ha risposto male, mi ha fatto venire la mosca al naso, e gli ho tirato uno schiaffo’ - ‘When Giacomo replied rudely to me, made me mad and I slap him!

From Latin PISCIS

ESSERE SANO COME UN PESCE - to be as healthy as a fish

NUOTARE COME UN PESCE - to swim like a fish, to be a perfect swimmer

NON ESSERE NE’ CARNE NE’ PESC - to be neither meat or fish, to be in between, to not have a specific flavor, personality, etc

ANDARE A FARE COMPAGNIA AI PESCI - to go keep company to the fish, to drown

NON SAPERE CHE PESCI PRENDERE - literally not knowing which fish to catch, to fish, to have ran out of options, therefore being uncertain about a the future 

‘Non riesco a trovare a trovare lavoro! Ho provato dappertutto! Non so più che pesci prendere’
 ‘I can’t find a job, I tried everywhere, I don’t know what to fish anymore!

ESSERE COME UN PESCE FUOR D’ACQUA, to feel like a fish outside the water, very uncomfortable

‘Mamma mia, ieri alla festa mi sono sentita un pesce fuor d’acqua! Erano tutti dottori e scienziati e non sapevo neanche di cosa parlassero!' 
‘Oh my God, last night at the party I felt like a fish out of the water(out of its element) they were all scientists and doctors and I didn’t even know what they were talking about’

TRATTARE QUALCUNO A PESCI FACCIA, to slap somebody with a fish, to treat them BADLY

‘Wow, sono andata in banca per chiedere un prestito, e mi hanno trattata a pesci in faccia’

‘Wow, I went to the bank to ask for a loan, and they treated me horribly’

CHI DORME NON PIGLIA PESCI, the one who sleeps doesn’t catch fish

ESSERE MUTO COME UN PESCE, to be as mute as a fish, won’t talk, won’t reveal a secret

BUTTARSI a PESCE, to throw yourself as a fish into something or into doing something 

‘Ha cominciato il nuovo lavoro ci si è buttato a pesce’ ‘He started a new job and thew himself in it, like a fish’

FARE L’OCCHIO A PESCE MORTO, to give the dead fish eye, which, despite what the image would suggest, refers to looking at somebody in a seductive// very sweet way

PESCE D’ APRILE, what English speakers call April fool

L’OSPITE È COME IL PESCE: DOPO 3 GIORNI PUZZA, A guest is like fish, on the third day it starts to smell — can’t stay more than 3 days as a guest!