Hey,
I have done a series of lessons on Superhero's for grade 5/6 after school. It may work with grade 3/4 too. My lessons are 40 minutes long although the first class ended up going over two lessons. It covers using the sentences "he/ she is...", "he/ she wears..." and "he/she can..." and the vocab basic describing words, parts of superhero costumes, superhero skills and comic book language.
Lesson 1 (or maybe 1 & 2) - He/ She is a superhero (PPT, worksheet, guess who game)
Lesson 2 - He/ She wears (PPT, wordsearch, worksheet)
Lesson 3 - He/ She can (PPT, worksheet and charades)
Lesson 4 - Design a Superhero and write some basic sentences (PPT review then worksheet)
Lesson 5 - Make a Comic about your superhero (PPT then comic strip)
I made some wordsearches using
http://www.toolsforeducators.com and downloaded a blank comic strip from google images but I haven't uploaded those. Attached are some worksheets I have made.
Hope this is of use.
Matty.