Blue marionette was removed from RuneScape after an update, but still exists in-game for those who had obtained it.
Blue marionettes were available during the 2005 Christmas event. After obtaining the various Christmas hats and scarves from Diango's workshop, players could take five boxes of baubles to a huge tree in the centre of Varrock. If players examined the tree a message would appear in their text box saying the words "Ug loves Aga," an allusion to the Troll Romancequest. Players could use their boxes of baubles on the tree after which it would turn into a Christmas tree and a box would appear near the roots. Inside the box would be a marionette. Diango, located in Draynor Village, will replace any marionettes or holiday items you lose.
The marionette can be operated to do 4 different moves - jump, walk, dance and bow.