Que Cera?

Michael Cera, whose "Year One" opens Friday, is far from a leading- man type. The weird thing is, he's far from the only scrawny zero-charisma star.

Indeed, last month I had the strangest conversation with a friend. We were talking about "Adventureland" and she told me how much she liked Michael Cera. I told her Michael Cera was not in "Adventureland."

"He was," she said.

"No, you're thinking of Jesse Eisenberg," I said.

Turns out, she's not alone -- confusing Michael Cera with other lilting man-boy actors of the moment is a concern.

And because you have too much going on in your life to know which actor is Michael Cera, here's a cheat sheet:

Age: 20.

Why you think he's Michael Cera: No. 1, he is Michael Cera. Also, he is physically negligible, a rail-thin angelic man-boy with big, earnest eyes who has probably had the same haircut since third grade; he stammers when he tries to talk to women, or to almost anyone, the mark of a true sensitive high school intellectual (in movies, at least); his default expression is gape-mouthed profound bewilderment, with grace notes of adolescent stupidity and subdued teenage frustration.

Why he's not Michael Cera: Does not apply.

Age: 24.

Where you've seen him: As the son who won't talk in "Little Miss Sunshine," as the preacher with pretensions who spars against Daniel Day-Lewis in "There Will Be Blood" and soon in "Taking Woodstock."

Why you think he's Michael Cera: He's thin and pale; his voice breaks when he gets excited; he's eerily placid.

Age: 20.

Where you've seen him: As Chekov in "Star Trek"; as teenager Kyle Reese, future father of John Connor in "Terminator Salvation," and as the kidnapped boy in "Alpha Dog."

Why you think he's Michael Cera: Like Cera, if cast in a World War II drama, he could easily play the young soldier who represents the death of innocence: boyish face, severely pale skin, slight in appearance, deer-in-headlight eyes.

Why he's not Michael Cera: Rarely mugs; his delivery rests more on short bursts of misplaced overconfidence than awkward hesitation.

Age: 25.

Why you think he's Michael Cera: Like Cera, his niche is Indie With Poignant Laughs. And your first reaction is not whether he is an actor, but whether he is that guy you've never heard of whom you agreed to friend on Facebook. His skin is translucent; his eyes are wide. His delivery is pure hesitation, followed by a spew of words.