We are going to create a single-page web app that contains an inline SVG illustration of a pelican riding a bicycle.
 The entire app will be in one file: index.html, with the SVG embedded inline.
 We'll use a <style> tag for CSS and a <script> tag for any JavaScript, but note that the task is just an illustration, so we might not need JavaScript.
 Since the requirement is to have a self-contained file, we will not use any external resources.

 Let's break down the illustration:
 - A pelican: large beak, webbed feet, wings, etc.
 - A bicycle: frame, wheels, pedals, handlebars, etc.

 We'll create the SVG with appropriate shapes and paths to represent the pelican and the bicycle.

 Steps:
 1. Set up the basic HTML structure.
 2. Create an SVG element with a viewBox that gives us enough space to draw.
 3. Design the bicycle: two wheels, frame, pedals, chain, handlebars, seat.
 4. Design the pelican: body, head, large beak, wings, webbed feet, and position it on the bicycle seat.

 We'll use simple shapes and paths for the illustration. We can use circles for wheels, lines for the frame, and paths for more complex shapes.

 Let's decide on a viewBox. We can use something like "0 0 800 400" to have a wide aspect ratio.

 We'll draw the bicycle first and then the pelican on top.

 Since we are creating an illustration, we can use a cartoonish style.

 Let's start by writing the HTML file with the SVG inside.

I've created a complete single-page web app with an inline SVG illustration of a pelican riding a bicycle. The file `index.html` contains:

**Features:**
- A colorful illustration of a pelican riding a bicycle
- Animated wing flapping using JavaScript
- Sky background with sun and clouds
- Green ground with road markings
- Trees in the background
- Styled container with shadow effects
- Responsive design that works on different screen sizes

**Key SVG elements:**
- Pelican body with distinctive beak and wing
- Bicycle with frame, wheels, pedals, and handlebar
- Pelican's feet positioned on the pedals
- Road lines and background scenery
- Fun \"PEDAL POWER!\" text

The illustration is fully self-contained with no external dependencies - all CSS and JavaScript are inline. The pelican's wing gently flaps to add some animation, and the overall design is playful and colorful.