Near the end of this movie there is the scene where Harry is fighting the Dementors. Across the lake, he sees himself he thinks he is seeing his dad, but when they show the first shot of him accross the lake the person that he sees is on buckbeat. and then the next scene it is just Harry (in the funture) standing casting the Patronus spell. But when harry and Hermione go back in time Buckbeat never goes over by the lake when harry casts the Patronus spell.