sneak up on

sneak up (on someone or something)

1. To approach someone or something in a sneaky, furtive manner so as not to be noticed. Don't sneak up on me like that—you frightened the life out of me! We don't want the guards to see us, so we'll need to sneak up from the back.
2. To come up on someone or some group gradually or without being noticed. I've been so busy with my work that our wedding anniversary completely snuck up on me. The deadline is sneaking up on us, and we still haven't made any substantial progress.
See also: sneak, someone, up
Farlex Dictionary of Idioms.

sneak up on someone or something

to approach someone or something quietly and in secret. Please don't sneak up on me like that. I sneaked up on the cake, hoping no one would see me. someone did.
See also: on, sneak, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • sneak up
  • sneak up (on someone or something)
  • slip up on
  • slip up on (someone or something)
  • steal up on
  • steal up on (someone or something)
  • sneak out
  • sneak out (of some place)
  • spies
  • spy on (someone or something)
References in periodicals archive
Stress can sneak up on you, so try to notice the signs before it spirals out of control.
Stress much? Imagine not feeling totally rushed, tired, cranky and overwhelmed this year. It's possible! Really
Not surprisingly, we find a lot more quotable anthropology, philosophy, or theology in Cathy," "Calvin and Hobbes," "The Far Side," or "Doonesbury" than "Batman" or "Brenda Starr." The reason for this seems fairly simple to me--the things we joke about or lampoon are often the very issues we feel the strongest about, and not infrequently humor, whether light or biting, is the only way we know to sneak up on the really important questions of life.
The art-parables of the funnies don't just sneak up on us because they're humorous but also because they look so unimportant.
See you in the funny papers