I have been setting expressions to music and rhythmic chants for decades with excellent results.
What did you do today? is an action song for kids, which, through repetition, teaches the question form in the past simple tense, the answer with relative prepositions, shop vocabulary, infinitive of purpose and prepositions with transport.
The idea is that you fix these expressions through repetitive chants so that they flow from your mouth spontaneously when you are speaking, without having to think.
After having written and recorded a video of the song I realised it contradicts my lessons on the Present Perfect Tense always being used with 'today', 'this week' etc. and according to the grammar books you shouldn't use 'today' with the Simple Past Tense. This proves that a language is alive and more flexible than the rigid rules of a grammar book because the sentence is completely natural and widely used. The explanation lies in the fact that this question is asked at the end of the day when the events have already taken place and therefore are considered to be in a period which is completely finished, therefore using the Simple Past Tense despite the word 'today'.
I hope you have fun with this repetitive chant.
You can download the worksheet to the song below.
Hope it's useful!