During the months Percy was gone, Tyson and Grover developed a very, well, strange friendship. They were still half scared of each other, but put their fears aside to help in the effort to find their leader.
The two had ended up going on a mini quest to investigate an apparent sighting of a black haired, green eyed boy in New Jersey, where they'd bonded even further. As soon as Tyson found out about Grover's love for tin cans, he'd forged him an everlasting one. Grover had also discovered Tyson's undying love for horses, and had invited one of Juniper's, fourth cousin's, three times removed's extra large unicorns to come see him as a vacation.
However, they loved nothing more than cheesy, gooey, vegetarian pizza, and went through countless numbers of them during the quest.