Andy wants to be the new Tom Hanks, who voiced Woody in Toy Story, in which the child he belonged to was named Andy, and Woody had Andy's name written on his boot.
"Cowabunga" is an exclamation thought to originate from The Howdy Doody Show. It was later popularized in the surfing community, perhaps due to its similarity to the Hawaiian "kupaianaha," a joyful exclamation of surprise. Snoopy from Peanuts used the expression in the surfing context in 1965. The Cookie Monster from Sesame Street used the phrase in the 1970s and '80s. Finally, Michelangelo from Teenage Mutant Ninja Turtles (1987) reintroduced "cowabunga" in its most popular incarnation yet, which spawned merchandise with the word and influenced its use by Bart Simpson on The Simpsons and as a tagline for Disney's 2002 film Lilo & Stitch, set in Hawaii.
When Andy drinks from Cal's flask against Cal's orders, Cal says it was behavior more like Robert Downey, Jr. rather than Tom Hanks, which Andy accepts as a compliment. Before launching a comeback as the start of Iron Man, Robert Downey, Jr. had burned many bridges in Hollywood due to his substance abuse problems.
References the old Hollywood concept of having "it," an intangible x-factor that defines a star.
"Cowabunga" is associated with the surfing community, which is not as widespread in California as it is in Hawaii. However, stereotypes about Californians often hearken back to the surfing scene, which is why the character Cal uses "cowabunga" as an appropriate word for Andy to learn to sound like a Californian. Despite having nothing to do with cows, Cal then suggests that "happy cows come from California" as a way to remember it.