What clues would one look for to spot a Cali accent, generally? What was it about Padelacki's speech that aroused your suspicion?
Shortened syllables and dropped consonants, I think. An intersyllabic /t/ tends to shift from the palatal stop that I'd use to a tongue flap and then to nothing, as when he says "It kine-uh made it sink in." I recently noticed that one of my southern Californian nephews says "impord-n'" where I say "impor'n'" for
important. (I wish I could transcribe these words in IPA, sorry!)
Southern Californian Anglos really don't have a very distinctive accent; they tend to speak with one end of the general American accent. Unsurprisingly, Latinos often have a Mexican Spanish-influenced accent. Many Blacks have an accent influenced by African-American Vernacular English, with roots in the deep South (the geographical Southeast) where their ancestors lived if they don't live there themselves. That's far from universal in that community, though; if you've heard the newly-famous
Amanda Gordon, you may have noticed that she doesn't have much of that accent. She attended my nephew's high school and recited a poem at their graduation, which I attended. Alas, it apparently didn't make a deep impression on me — I don't remember the recitation at all.