I just discovered one for me.... I am definitely a person who uses "filler" words when talking (not so much when writing). I say, "ok" and "you know" and "let's see" and so on...
So I often hear Spanish-speakers saying the same thing as a filler word, and I always thought it was "haber", which really has made absolutely NO sense to me whatsoever. Hahaha!! I just realized that it's "a ver", as in "let's see". Exactly what I would say in English. NOW it makes sense! LOL!!!