From Disney's Hollywood Studios Wiki
Luxo Jr. is an Audio-Animatronic Lamp that hops on a ledge on Pixar Place directly across from Toy Story Midway Mania! Luxo is currently in "preview mode" meaning he comes out sporadically, and there are days he may not come out at all.
 About the Character
Luxo Jr. Made his first appearance in an early Pixar short named after him. In the short, Luxo Jr. and a taller lamp (persumingly Luxo Sr.) are standing around, and Jr. goes off and finds a ball to play with (the yellow ball with a blue strip and red star that has been featured in every Pixar Film), but eventually pops the ball by jumping on it (like he does to the letter "I" in the Pixar logo) much to his father's dismay. Jr. walks off sad only to find a larger ball to play with.
The short was one of the first CG shorts, and quickly became a hit, making Luxo Jr. part of the company logo.
 Shows Synopsis
Luxo has two distinctive shows depending on what time of day it is.
 Day Show
Luxo hops out and different styles of music begins to play, to which he dances. Among the selection they play the Waltz, where he spins around, Disco, which he a Saturday Night Fever move, and Polka, to which he refuses to Dance and shakes his head. "You've Got a Friend in Me" begins to play and he starts dancing again, and than he takes a bow and returns.
 Night Show
The lights on the streets of Pixar Place go dim, and than Luxo hops out with his light shining bright. He starts looking around and looks at a nearby tree, when suddenly it lights up and place a musical note. Luxo is surprised and tests to see if it happens every time, which it does, and than realize that any tree he looks at does a similar thing, just with a different sound and color light. He than conducts his own version of "You've Got a Friend in Me" with the trees, with all of Pixar Place lighting up when he does so. After the song is completed, he takes a big bow, returns to his home, and the lights on the streets come back on.