Μακραὶ τυράννων χεῖρες.
Long (are) the hands of tyrants.
Compare the English proverb, "Kings have long arms." In other words, kings, tyrants, etc. can exert their dangerous power at a distance. And yes, the English word "tyrant" comes from the Greek. Compare an expanded version in Benjamin Franklin's Poor Richard's Almanac: "Kings have long Arms, but Misfortune longer: Let none think themselves out of her Reach."
Λωτοῦ ἔφαγες.
You've eaten from the lotus.
In other words, you're high! After eating the narcotic lotus, you're lost in a cloud of forgetfulness, not doing the things you should. The mythological "lotus-eaters" (λωτοφάγοι) forgot everything, even their homes and families. You can find out more at Wikipedia: Lotus-Eaters.
Λέγε εἰδώς.
Speak what you know.
Literally, "having come to know something, speak." The word εἰδώς is the perfect active participle of οἶδα. This is another one of the sayings attributed to the Seven Sages; see more at Wikipedia: Delphic maxims.
Ὅμοιος ὁμοίῳ.
Like to like.
This is a widely used ancient Greek saying; in Plato's Gorgias, Socrates calls it an old and wise saying. An expanded version including a verb is: Ὅμοιος ὁμοίῳ ἀεὶ πελάζει, "Like always approaches to like." Compare the English saying "birds of a feather (stick together)" or "a man is known by the company he keeps." The Greek root ὁμοιο- shows up in English words like homeostasis and homeopathic.
Ἥλιξ ἥλικα τέρπει.
People of the same age enjoy (each other's company).
Literally, "same-age delights in same-age." This saying appears in Aristotle's Eudemian Ethics in a discussion of friendship, and he marks the expression as proverbial with the word λέγεται, "it is said that" — λέγεται ἥλιξ ἥλικα τέρπει. You can see the root τερπ in the names Εὐτέρπη, the muse of music, and Τερψιχόρη, the muse of dancing. And note, Greek ἥλιξ is not the origin of English "helix," which instead comes from Greek ἕλιξ, meaning "something twisted, a spiral."
And to finish up, here's a random proverb and a random LOLCat too: