Snot on a Wire

From Say What? Talk Like a Local Without Putting Your Foot In It, a dictionary of translated idioms published by Lonely Planet in 2004. 

Kick the bucket

German: Den Löffel abgeben / To give away the spoon
Czech: Natáhnout Baèkory / To stretch the slippers
Swedish: Att trilla av pinnen / To fall off the stick
Latvian: Nolikt karoti / To put down the spoon
Dutch: Het hoekje omgaan / To go around the corner
Danish: Stille træskoene / To leave your clogs behind

Shake like a leaf

Czech: Chvit sejak osika / To be moving like an aspen tree
Latvian: Ka punkis us drats / Like snot on a wire

When pigs fly

French: Quand les poules auront des dents / When hens have teeth
Spanish: Cuando las ranas crien pelo / When frogs grow hair
Russian: Kag-da rak svist-myet / When the crayfish whistles
Turkish: Balik aðaca / When fish climb trees
Filipino: Pagputi ng uwak / When the crow turns white
Finnish: Kun lehmät lentää / When cows fly

When hell freezes over

Croatian: Kad na vrbi rodi grozdie / When grapes ripen on the willow
Dutch: As Pasen en Pinksteren op één dag vallen / When Easter and Pentecost are on the same day
German: Wenn es im Sommer schneit / When it snows in summer
Italian: Nella settimana dei due giovedì / In the week with two Thursdays
Spanish: El dia del arquero / Goalkeeper’s day
Slovenian: Ob svetem nikoli / On Saint Never’s Day
Portuguese: No dia de São Nunca / On Saint Never’s Day

It’s all Greek to me

German: Ich verstehe nur Bahnhof / It’s all railway station to me
Czech: Je to pro mne španelská vesnice / It’s a Spanish village to me
French: C’est du chinois / It’s Chinese