Most big businesses and brands are so protective of their logo, with strict guidelines for its usage but not Google. Google seems to have so much confidence in the strength of their brand that they absolutely deconstruct it sometimes several times a week. The Google homepage logo that changes is known as the Google Doodle.
To have Google choose to promote your art, music, body of work, creativity, business, product or person is an incredible coup as far as creating awareness and buzz (because of their amazing reach – for instance, Google has 95% market share in Australia which means millions of unique visitors every day who will see the Google Doodle), but its also an incredible honour.
I absolutely love that Google honors inspiring people, artists, musicians and creativity by changing their standard Google Homepage Logo with a “doodle” on significant days. Some of my favourites have been the Star Trek one (and I’m not even a fan of the TV show), sesame street brought a smile to my face, as did the tribute to the incredible trumpeter Dizzy Gillespie (I played the trumpet all through school and even got to play in the Sydney Opera House, twice).
Some of the Google homepage Doodles didn’t make sense to me immediately, but my husband would explain the history of the Fender guitar and then I learn something new about Les Paul.
Some are simply cute and remind me of my childhood, like the Hungry Catapillar books or Pacman. But you get my point, I love that Google has enough confidence in its own brand and its brand recall and that they are creative enough to use their brand to pay homage to the brands that they love and are inspired by. 
