Because, amigo, Leo the Fart was very, very fat.
6 seconds sound clip from the Last Action Hero movie soundboard.
You can hear this line at 01:06:09 in the Blu-ray version of the movie.
Quote context
[...]
- Funeral?
- Right.
- Wrong.
- Who took the shot? Was it Benedict? Most likely.
- Would he miss? No way. Unless he wanted to miss.
- You're saying he meant to miss? Why?
- Because, amigo, Leo the Fart was very, very fat.
- Get it?
- They broke in last night. They cut Leo open like a turkey, stuffed him with TNT...
- He goes off at the funeral and takes out the entire Torelli mob, all at once.
- Vivaldi owns the town. That's what all this has been about.
- Vivaldi's going to blow up that funeral.
[...]