From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
“Welcome, welcome!☆ Today's dinner is the... Mushroom Full Course!☆”
The Toad waitress is a Toad who works on the Excess Express in Paper Mario: The Thousand-Year Door. Her name is never revealed. During the Mario team's trip to Poshley Heights in their quest for the Garnet Star, her Shell Earrings are stolen by Doopliss (disguised as Zip Toad). The Shadow Sirens planned to mix the Shell Earrings with Toodles's Gold Ring and some Nitro Honey Syrup to set off an explosion, destroying the train and fulfilling the "sticky, yummy doom" Mario had been warned of. After Mario and friends catch him, their plan fails. Mario can optionally return the Shell Earrings to the Toad waitress, for which she will give Mario a Star Piece as a reward. She remains on the Excess Express for the rest of the game.
The Toad waitress's Shell Earrings were given to her by her ex-boyfriend, an unnamed Squeek Mario can speak to in Podley's Place. The Toad waitress often uses star symbols in her text and speaks in a hyperactive, line-by-line sequence. According to Goombella, she probably isn't a very good waitress, but likely attracts many men.