D.Vader: You guys have different costumes for different occasions?!
Sigh-Fi
A generalist Sci-Fi meme community.
The Memiverse:
!90s_memes@quokk.au
!y2k_memes@quokk.au
!philosophymemes@quokk.au
otoh, when did we see Vader at a formal occasion?

There was that grand feast on Bespin. Didn't even try to dress up after inviting his daughter and her boyfriend to dinner.
He visited a Death Star as an envoy a few times...
He was present for the arrival of the emperor in Ep. VI, where dozens of stormtroopers stood at attention aside red carpet... Seems kinda formal.
...and the Stormtroopers wore their regular armor.
I'd guess that the Empire is not unlike the British, where the Redcoats wore the same thing in battle as they did to a formal dinner.

Chewy [translated]: You guys have clothes?
I don’t know what this shot is from - in this scene in the film Luke is wearing a yellow leather jacket
Also both brought blasters to an awards ceremony
An awards ceremony is the perfect opportunity for a villainous attack!
Chewie, on the other hand, put on a white suit and did the John Travolta dance from Saturday Night Fever. What a legend.