EXCLUSIVE

1st class plane tickets ... endless filet mignon ... her own king-sized bed ... 5-figure paychecks ... and that's just a tiny glimpse into the ridiculous life of the Internet sensation known as Grumpy Cat.

The cat's manager -- yes, she has one -- tells TMZ, the famous feline is in Austin, TX this week to shoot commercials for Friskies (the cat's sponsor) and to appear at the SXSW Interactive festival.

Grumpy flew first class ... and she's been living it up ... with her own, full-time assistant to brush her, an endless supply of Friskies as well as other treats, bottled water and her very own room at a four-diamond hotel ... king-sized bed included.

And to get around Austin ... Grumpy has her own chauffeur.