Kelvin Banks Jr. is going to need a few napkins to go along with his new Saints jersey ... 'cause the former Texas star's baby upchucked all over the place -- right as New Orleans was drafting the offensive lineman!!
The hilarious scene just unfolded as Roger Goodell was reading off the ex-Longhorn's name out at Lambeau Field.
Check it out ... Banks Jr. was celebrating the selection with his family from a remote location -- and there was so much excitement in the room, his little one vomited all over Mom.