This is a trailer for a film from the same makers of 2014's The Lego Movie, which was rated U. This film has also been passed at U and contains mild comic violence, rude humour and very mild bad language. Warner Brothers have submitted several trailers for the film to the BBFC. This trailer was submitted with a U request. Watch the trailer, make a note of the issues and suggest a category before comparing your decision and reasoning to that of a BBFC Compliance Officer - the person who watches the film and decides on the rating.
Even if you have seen The Lego Movie, it’s possible that members of the audience might not have done. Remember that trailers do not always receive the same rating as the features they are advertising. This is because the viewing experience of trailers is different – trailers come unbidden to audiences who may have elected to see a very different kind of film.