She's Optimus Prime: Seyfried offers something a little different: she’s hot in a floaty, pretty way rather than Fox’s full-on sizzle, and after a solid record of lower profile films she’s ready for a crack at a summer tentpole.
Wrong like Megatron: Audiences may shy away precisely because she is different to Fox – especially with Jennifer’s Body, which starred the pair together and played on Seyfried’s nerdier look, fresh in the memory.
She's Optimus Prime: A genuine contender. The Brit starlet is currently riding a wave of blockbusters that includes Quantum Of Solace, Clash Of The Titans and Prince Of Persia, and that doesn’t look like breaking just yet.
Wrong like Megatron: Arterton has the leggy looks, but does she have the glamour? It’s a long, long way from Gravesend to LA, and she’ll struggle to vamp it up like Fox.
She's Optimus Prime: Another post-franchise starlet primed for a pop at the big time. Hudgens would offer a different chemistry with co-star Shia LaBeouf, giving him more giggles and drama to bounce off.
Wrong like Megatron: It might be too late for her to ride straight into a triple-A deal – High School Musical was a couple of years ago, and it’s been quiet for Hudgens since.
She's Optimus Prime: Saldana is smoking hot, super confident and has some of the same imposing physical presence as the departing Fox. Plus, with her blockbuster experience from Star Trek and the mighty Avatar, she knows her way around a green screen.
Wrong like Megatron: Despicable though it might be, by Hollywood standards Saldana may be too old to play against Shia LaBeouf, with her 31 and he still just 23.
She's Optimus Prime: A leftfield choice, but Diaz would bring a freshness and – who knows? – even some acting to the role. Her CV is littered with sparky parts in well-regarded indie flicks…
Wrong like Megatron: Things have been quiet for Diaz lately, and it doesn’t seem likely that Bay and pals will plump for thesping skills over box office bills.
Mary Elizabeth Winstead
She's Optimus Prime: We can really see this one. Winstead has the looks and the experience, but also a softer quality than Fox – a twinkling smile that could give her potential partnership with Shia LaBeouf a splash of pizazz.
Wrong like Megatron: The only real snag would be Winstead casting off her scream-queen tag, earned through the likes of The Ring Two, Final Destination 3 and Grindhouse.
She's Optimus Prime: Not only is Mulligan completely adorable, she's been picking up serious press Stateside, and is currently dating prospective co-star Shia LaBeouf.
Wrong like Megatron: Aside from being insanely pretty and dating Shia, she’s basically wrong for it in every way possible. Depends on how much sway her potential co-star has with boss-man Bay.
She's Optimus Prime: The Twilight series has given Stewart a platform of notoriety and box office success that’ll surely mean she ends up leading a blockbuster sooner rather than later.
Wrong like Megatron: But is it too soon, with commitments to the tween horror phenomenon still very active? And is she a bit too moody? And a lot too typecast?
She's Optimus Prime: Another choice that would give the new sequel a little edge – the indie princess is cute as a button, and could match Shia for laughs.
Wrong like Megatron: Judging by the smart, edgy projects she’s undertaken in her short career, she'd rather fight a real-life giant robot than co-star with a bunch of them.
She's Optimus Prime: She might play second fiddle to Kristen Stewart in the Twilight flicks, but Greene is hotter and more watchable than her co-star, and has received just as big a profile boost.
Wrong like Megatron: Not the biggest name on the list. And besides, rumours are she’s being lined up for Scream 4…