What's up with Bahamut?

[Enkidoh]

That's consistant with Bahamut's appearence though throughout the FF series where in most FF games he's usually more bipedal than serpentine.

But also remember the Primal Bahamut is a bastardization of what the real Bahamut looked like, so there might have been some liberties with the appearence based on Tiamat's thoughts when he was first summoned (after all, Tiamat was so horrified by the result she allowed herself to be captured by the Allag and remained in confinement on Azys Lla for thousands of years simply as penance for disrespecting Bahamut's memory).

Primals rarely perfectly capture the image of what the summoner has in mind, especially if it's referencing an actual person or entity (another example is the Primal Shiva looking nothing like the historical Shiva Hraesvelgar fell in love with).

[Anonymoose]

Did his summoning make him look funny and that's just his primal form

Primal Bahamut is a bastardization of what the real Bahamut looked like

His representation on the Celestial Dragons poster is probably closer to what he really looked like, which is closer to what you'd expect based on his siblings. Nidhogg, Hraesvelgr, Tiamat, and (it looks like so far) Vrtra all share the same in-game model skeleton with different customizations. Even the "true" Midgardsormr in Omega seemed to.

[Jandor]

Primals rarely perfectly capture the image of what the summoner has in mind

That collection of oddballs we squeezed out of Eden spring to mind.

People thought it was the WoL taking too many blows to the head, but that's just how summoning is.