Hint Toad

Blue Toad (named Hint Toad in Super Mario Odyssey ) is one of the five members of the Toad Brigade, who acts as Princess Peach's attendants and royal guards. He is the smartest member of the brigade and often helps Mario with the use of his knowledge.

Super Mario Galaxy
In Super Mario Galaxy, Blue Toad appears as one of the five members in the Toad Brigade. Eventually, Mario comes along and saves the five Toads (including Blue Toad) in the Honeyhive Galaxy. Throughout the game, the Toad Brigade attempts to help Mario on his quest by traveling throughout the different galaxies in the search for Power Stars. In their last game appearance, the five Toads are revealed to have been promoted to Royal Guards due to their work of helping Mario.

Of the Toad Brigade, Blue Toad is shown to be the smartest of the five Toads and has provided Mario with some very useful information about the galaxies. To show his intelligence, Blue Toad appears wearing glasses in this game and is called the "smart one".

Super Mario Galaxy 2
Blue Toad is once again part of the Toad Brigade in Super Mario Galaxy 2. He, along with the other Toads in the brigade, arrives on Starship Mario after Mario clears Spin-Dig Galaxy. Once again, he is the smartest, and often gives Mario hints on how to defeat Bowser. His speech changes every time Mario clears a world.

Captain Toad: Treasure Tracker
Blue Toad appears in Captain Toad: Treasure Tracker. He appears in some levels and will give Captain Toad a Super Gem, Super Mushrooms, or 1-Up Mushrooms when found. He seems to lead Yellow Toad and Bank Toad, suggesting he may be second in command. His appearance is similar to how he appeared in the Super Mario Galaxy titles with his signature pair of glasses. However, he now sports an explorer suit and backpack for collecting treasure much like the Captain himself.

He also helps the Captain in other missions such as following him around alongside the other members of the Toad Brigade for unlocking various secrets and helping Captain Toad obtain a Power Star. Prior to the final fight against Wingo, Blue Toad tosses a Super Mushroom to Captain Toad as he climbs to the peak of the tower to fight the bird in order to assist the Captain.

Super Mario Odyssey
Blue Toad, now known as Hint Toad, appears in Super Mario Odyssey as a helper character. He appears alongside Uncle amiibo to help Mario locate Power Moons scattered in every kingdom. Unlike Uncle amiibo, he charges Mario 50 yellow coins for every Power Moon location.

Trivia

 * Blue Toad shares many similar characteristics and looks similar to the characters Toadbert and Russ T. as they are all blue-spotted Toads, are intelligent, and wear glasses.
 * In Super Mario Galaxy 2, after giving the Banktoad 1000 Star Bits, he will wear a pair of glasses similar to Blue Toad's pair because he wants to look smart.
 * In Super Mario Galaxy 2, in the Boulder Bowl Galaxy, the Blue Toad will be picking at the ground with a pickaxe. He says he lost his glasses, but upon closer examination using the first-person view, he is actually hitting his glasses with his pick.